Arctic Sea Ice : Forum

Cryosphere => Antarctica => Topic started by: Lord M Vader on June 20, 2014, 05:05:33 PM

Title: Will Antarctica sea ice set a new record in 2014?
Post by: Lord M Vader on June 20, 2014, 05:05:33 PM
While our main focus have been on the sea ice in the Arctic regions and whether this melt season will end up close to 2010-2012 and 2007 things are quite interesting on Antarctica. Bremen have estimated the sea ice in Antarctica to be the highest on record for this time at year and above 2010 http://www.iup.uni-bremen.de:8084/amsr2/extent_s_running_mean_amsr2_previous.png (http://www.iup.uni-bremen.de:8084/amsr2/extent_s_running_mean_amsr2_previous.png). Meanwhile, Cryosphere Today seems to concur about this. The anomaly are right now one of the absolutely highest ever, reaching 1,692 Mn km2 above the normal from 1979-2008. While records have been shattered in Arctic the same have been true for Antarctica but on the opposite side. both minimas and maximas there have been the highest on record there for the last couple of years.

Antarctica sea ice doesn't get the same attention due to that the sea ice there for example use to be thinner and younger. The sea ice there also have a higher occurrence to be affected by the strong winds pounding the continent almost infinitely.. And it doesn't have the same effects on the global climate as the sea ice in Arctic does..

But nonetheless, it will be interesting to see if there will be a new september sea ice maxima record this year. What do you guys think?

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.iup.uni-bremen.de%3A8084%2Famsr2%2Fextent_s_running_mean_amsr2_previous.png&hash=7b16103cf5bb2694834961a7f4adc6fc)

Source: University of Bremen.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 12:07:32 AM
LMV,
I would guess that most people would agree that in 2014 the Antarctic Sea Ice Extent will most likely reach a maximum value, as I certainly do.  In this regards I provide the following linked reference that indicates that on average the Antarctic Sea Ice Area is going up by 0.2% per year, and the average thickness is going up 0.2% per year, resulting in an average sea ice volume increase of 0.4% per year.  However, these numbers are orders of magnitude lower than the corresponding changes taking place to the Arctic Sea Ice.  Furthermore, please note that the reference demonstrates that: "Ice thickness increases are also found in the inner pack in the Amundsen and Weddell Seas, where the model suggests that observed ice-drift trends directed toward the coast have caused dynamical thickening in autumn and winter. Modeled changes are predominantly dynamic in origin in the Pacific sector and thermodynamic elsewhere."

Holland, Paul R., Nicolas Bruneau, Clare Enright, Martin Losch, Nathan T. Kurtz, Ron Kwok, (2014), "Modeled Trends in Antarctic Sea Ice Thickness", J. Climate, 27, 3784–3801,  doi: http://dx.doi.org/10.1175/JCLI-D-13-00301.1 (http://dx.doi.org/10.1175/JCLI-D-13-00301.1)


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00301.1?af=R (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00301.1?af=R)


Abstract: "Unlike the rapid sea ice losses reported in the Arctic, satellite observations show an overall increase in Antarctic sea ice concentration over recent decades. However, observations of decadal trends in Antarctic ice thickness, and hence ice volume, do not currently exist. In this study a model of the Southern Ocean and its sea ice, forced by atmospheric reanalyses, is used to assess 1992–2010 trends in ice thickness and volume. The model successfully reproduces observations of mean ice concentration, thickness, and drift, and decadal trends in ice concentration and drift, imparting some confidence in the hindcasted trends in ice thickness. The model suggests that overall Antarctic sea ice volume has increased by approximately 30 km3 yr−1 (0.4% yr−1) as an equal result of areal expansion (20 × 103 km2 yr−1 or 0.2% yr−1) and thickening (1.5 mm yr−1 or 0.2% yr−1). This ice volume increase is an order of magnitude smaller than the Arctic decrease, and about half the size of the increased freshwater supply from the Antarctic Ice Sheet. Similarly to the observed ice concentration trends, the small overall increase in modeled ice volume is actually the residual of much larger opposing regional trends. Thickness changes near the ice edge follow observed concentration changes, with increasing concentration corresponding to increased thickness. Ice thickness increases are also found in the inner pack in the Amundsen and Weddell Seas, where the model suggests that observed ice-drift trends directed toward the coast have caused dynamical thickening in autumn and winter. Modeled changes are predominantly dynamic in origin in the Pacific sector and thermodynamic elsewhere."

Therefore, taken at face value, there is little to discuss in this thread, unless denialist intend to claim (incorrectly) that a maximum Antarctic Sea Ice Extent record in 2014 means that global warming is not occurring.  If any denialists care to make such a claim in this thread, I hope that they are prepared to back-up any such claim with facts, as it has already been clearly demonstrated that the increase in Antarctic Sea Ice is related to such positive feedback mechanisms for global warming as: (a) the increase in the westerly wind velocities that causes the sea ice to both spread, and raft; but which also causes CO₂ venting from the Southern Ocean and the advection of warm CDW to contribute to grounded ice mass loss (which contributes to SLR); (b) the freshening of the Southern Ocean surface waters (largely associated with ice sheet/shelf ice mass loss, and increased precipitation); and (c) the reduction in the rate of AABW production.

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Anne on June 21, 2014, 02:40:00 AM
<snip>
Therefore, taken at face value, there is little to discuss in this thread, unless denialist intend to claim (incorrectly) that a maximum Antarctic Sea Ice Extent record in 2014 means that global warming is not occurring.  If any denialists care to make such a claim in this thread, I hope that they are prepared to back-up any such claim with facts, as it has already been clearly demonstrated that the increase in Antarctic Sea Ice is related to such positive feedback mechanisms for global warming as: (a) the increase in the westerly wind velocities that causes the sea ice to both spread, and raft; but which also causes CO₂ venting from the Southern Ocean and the advection of warm CDW to contribute to grounded ice mass loss (which contributes to SLR); (b) the freshening of the Southern Ocean surface waters (largely associated with ice sheet/shelf ice mass loss, and increased precipitation); and (c) the reduction in the rate of AABW production.

Best,
ASLR

The denialists do so claim, with boring regularity. They ignore that Antarctica is a continent with a totally different dynamic, a continent not a sea, that Antarctic sea ice melts out every spring. They have no idea where the sea ice comes from. They indulge themselves in a simplistic notion that North Pole=South Pole, yin balances yang and all's right with the world. Ignorance abounds and reproduces itself. ASLR, you have no idea of the ignorance out there. There are people to educate. Perhaps this thread can help do that.

ETA: There are probably a lot of people following this who aren't expert or even scientists, and who don't want to join in the discussions. This is an opportunity to speak to them.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 03:37:56 AM
Anne,

I have too many other things going on to provide a comprehensive post about the reasons that on average Antarctic Sea Ice is increasing (in area, extent, thickness and volume), so I will post a little at a time. 

Denialist should be aware that not only is the average water temperature in the Southern Ocean increasing with time, but also the air temperature above the Southern Ocean is increasing with time, and the following linked research makes it clear that the most significant reason why the Antarctic Sea Ice is increasing is due to the formation of the seasonal Antarctic ozone hole after the mid-1980's created by anthropologically induced chlorides in the upper atmosphere over Antarctica; which in turn caused the circumpolar Antarctic westerly wind velocity to increase (see the following abstract for the influence of this increased wind velocity on the Antarctic Sea Ice); and the linked reference indicates that the intensifying regional winds in Antarctic is one of the most significant factors accounting for the increasing maximum extent of Antarctic sea ice.

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00139.1?af=R (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00139.1?af=R)


Modeling the impact of wind intensification on Antarctic sea ice volume
By: Jinlun Zhang; Journal of Climate 2013 ; doi: http://dx.doi.org/10.1175/JCLI-D-12-00139.1 (http://dx.doi.org/10.1175/JCLI-D-12-00139.1)

Abstract
"A global sea ice-ocean model is used to examine the impact of wind intensification on Antarctic sea ice volume. Based on the NCEP/NCAR reanalysis data, there are increases in surface wind speed (0.13% yr−1) and convergence (0.66% yr−1) over the ice-covered areas of the Southern Ocean during the period 1979-2010. Driven by the intensifying winds, the model simulates an increase in sea ice speed, convergence, and shear deformation rate, which produces an increase in ridge ice production in the Southern Ocean (1.1% yr−1). The increased ridged ice production is mostly in the Weddell, Bellingshausen, Amundsen, and Ross Seas where an increase in wind convergence dominates. The increase in ridging production contributes to an increase in the volume of thick ice (thickness > 2 m) in the Southern Ocean, while the volumes of thin ice (thickness ≤ 1 m) and medium thick ice (1 m < thickness ≤ 2 m) remain unchanged over the period 1979-2010. The increase in thick ice leads to an increase in ice volume in the Southern Ocean, particularly in the southern Weddell Sea where a significant increase in ice concentration is observed. The simulated increase in either the thick ice volume (0.91% yr−1) or total ice volume (0.46% yr−1) is significantly greater than other ice parameters (simulated or observed) such as ice extent (0.14–0.21% yr−1) or ice area fraction (0.24–0.28% yr−1), suggesting that ice volume is a potentially strong measure of change."

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 04:03:07 AM
The following linked reference both notes that ice mass loss from Antarctic ice shelves also contributes (in addition to increased wind velocities) increased Antarctic Sea Ice Extent; and also disproves the idea that local atmospheric cooling is the source of this increase:


R. Bintanja, G. J. van Oldenborgh, S. S. Drijfhout, B. Wouters   & C. A. Katsman, (2013), "Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion", Nature Geoscience 6, 376–379, doi:10.1038/ngeo1767

http://www.nature.com/ngeo/journal/v6/n5/full/ngeo1767.html (http://www.nature.com/ngeo/journal/v6/n5/full/ngeo1767.html)

Abstract: "Changes in sea ice significantly modulate climate change because of its high reflective and strong insulating nature. In contrast to Arctic sea ice, sea ice surrounding Antarctica has expanded, with record extent in 2010. This ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling. Here we show that accelerated basal melting of Antarctic ice shelves is likely to have contributed significantly to sea-ice expansion. Specifically, we present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves. Simulating these processes in a coupled climate model we find that cool and fresh surface water from ice-shelf melt indeed leads to expanding sea ice in austral autumn and winter. This powerful negative feedback counteracts Southern Hemispheric atmospheric warming. Although changes in atmospheric dynamics most likely govern regional sea-ice trends, our analyses indicate that the overall sea-ice trend is dominated by increased ice-shelf melt. We suggest that cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 04:05:04 PM
In Reply #1 of this thread, I pointed out that the average Antarctic Sea Ice Extent was increasing even while the average air temperature over the Southern Ocean has also been increasing; which has been documented in the linked reference (with a free access pdf) by Zhang (2007), and see the abstract, and image captions, below.  The first image make it clear that the Pacific Sector surface air temperature is warming faster than the rest of the Antarctic sectors, which is bad news for sea level rise as the WAIS in the Pacific Sector is the primary source of Antarctic contribution to sea level rise.  The second image makes it clear that a lot of the sea ice thickening is occurring in the Weddell Sea Sector, most likely because warm CDW is getting under the FRIS and basal ice melting from these ice shelves is contributing directly to the formation of this thicker (and more extensive) sea ice in the Weddell Sea Sector, and is also contributing to a slow-down of the AABW production in this sector which use to sequester more CO2 into the deep ocean (but now the AABW absorbs less CO2).  The third image provides direct evidence that the average surface air temperature over the Southern Ocean is trending up, at the same time that the Antarctic Sea Ice Extent is trending up (meaning that the increasing sea ice extent is not related to some regional cooling of the atmosphere):

JINLUN ZHANG, (2007), "Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions"

http://psc.apl.washington.edu/zhang/Pubs/Zhang_Antarctic_20-11-2515.pdf (http://psc.apl.washington.edu/zhang/Pubs/Zhang_Antarctic_20-11-2515.pdf)

Abstract: "Estimates of sea ice extent based on satellite observations show an increasing Antarctic sea ice cover from 1979 to 2004 even though in situ observations show a prevailing warming trend in both the atmosphere and the ocean. This riddle is explored here using a global multicategory thickness and enthalpy distribution sea ice model coupled to an ocean model. Forced by the NCEP–NCAR reanalysis data, the model simulates an increase of 0.20 _ 1012 m3 yr_1 (1.0% yr_1) in total Antarctic sea ice volume and 0.084 _ 1012 m2 yr_1 (0.6% yr_1) in sea ice extent from 1979 to 2004 when the satellite observations show an increase of 0.027 _ 1012 m2 yr_1 (0.2% yr_1) in sea ice extent during the same period. The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass. This mechanism is the main reason why the Antarctic sea ice has increased in spite of warming conditions both above and below during the period 1979–2004 and the extended period 1948–2004."

Caption for the first Image: " Linear trend (1979–2004) of the NCEP–NCAR reanalysis surface air temperature over the ice-covered areas of the Southern Ocean defined as the 1979–2004 mean satellite-observed sea ice extent."

Caption for second Image: "1979–2004 mean model-simulated ice thickness and satellite-observed ice extent. The white line represents the satellite-observed ice edge with 0.15 ice concentration."

Caption for the third Image: "Surface air temperature over the ice-covered areas of the Southern Ocean (top). Sea ice extent, observed by satellite (bottom)."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 04:30:44 PM
The attached image from a 2002 National Geographic map of the Antarctic shows both the sea ice movement and the typical wind flow patterns (circa 2000 to 2001).  The sea ice movement indicates how both the Weddell and the Ross Sea areas manufacture and export sea ice (due to the wind push the extant sea ice northward exposing more leads that allow for more sea ice formation); while the wind pattern shows how some snowfall could be blown into the ocean.  It is important to note that circa 2060-2070 models project that the wind patterns will change (particularly in the Weddell Sea Sector), which will result in reduced sea ice formation (as opposed to the current trend for increasing sea ice formation):
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 04:41:53 PM
The 2002 National Geographic image that I posted in Reply #6 shows almost zero sea ice velocity in the Amundsen Sea area, which means limited lead formation by the ice moving north, which mean limited sea ice formation in this critical area

The accompanying image from the NSIDC shows the Antarctic sea ice extent on January 29, 2014 (during the austral summer).  It is worth noting that the sea ice extent in the ASE is below normal for this time of year, which implies that more storm and wave action can access the glaciers around the ASE, including PIIS, more easily than normal, potentially resulting in more calving than normal in this critical area.  Therefore, even though the average Antarctic Sea Ice Extent is trending upwards, where it counts (in the ASE) it is trending downward which will result in accelerating sea level rise contribution from the WAIS in the near (and long-term) future:
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 05:28:28 PM
While the NSIDC image in my last post was for only one season (austral summer of 2014), the attached image from the British Antarctic Survey, shows differences in Antarctic sea ice from 1979 to 2012; confirming that the Antarctic sea ice around the ASE is declining, which will expose the ice shelves in the ASE to more degradation from storm action:
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 06:11:06 PM
In the few year old linked NASA article on why the Antarctic Sea Ice Extent is growing.  The article cites numerous reasons, all of which probably make some contribution, with the changes in the Antarctic wind patterns associated with the ozone hole being the primary reason as indicated in the first attached image (see the captions below, also I note that the deepening of the atmospheric low pressure system in the Amundsen/Ross Sea area can also blow more warm CDW into the ASE resulting in more ice mass loss, see the first image).  The second attached image shows that the average reduction in Southern Ocean surface salinity is contributing to sea ice formation as this stratification of the Southern Ocean results in less mixing of the water, which leave warmer water below the surface, which leaves the ocean surface water cold and subject to freezing; however, it is important to note that this effect also leaves the warm CDW warmer than it used to be, which means that the advected warm CDW to the grounding line of Antarctic marine glaciers is warmer than normal, which caused accelerating grounding line retreat and accelerating SLR contribution particularly from the ASE glaciers (it should also be noted that less salinity sea ice is harder to melt than saltier sea ice, which together with the trend for increased Antarctic Sea Ice thickness, may account for why the minimum Antarctic Sea Ice Extent is also becoming higher during the austral summer).  The third image should that as there is a trend for greater precipitation in the Southern Ocean (which contributes to the freshening of the Southern Ocean surface water, together will ice mass loss from grounded ice sheets and from floating ice shelves); which results in more snow fall on the extant Antarctic Sea Ice, which causes the sea ice air draft to be reduced, which contributes to increased ocean water reaching the snow on the extant sea ice, which due to re-freezing leads to more snow-ice, which increases the thickness of the sea ice:

http://www.nasa.gov/topics/earth/features/antarctic_melting.html (http://www.nasa.gov/topics/earth/features/antarctic_melting.html)

Caption for first image: "Ozone depletion has caused more intense low pressure systems (shown in blue) to develop over the Amundsen and Ross Seas, while higher pressure systems (red) have developed on the periphery of the Southern Ocean. Ozone loss has likely strengthened the cyclonic wind flow across the Ross Ice Shelf and made winds cooler and stormier. Such changes can increase sea ice extent by pushing ice offshore and maintaining coastal polynyas (inset), areas of open water that tend to produce and export sea ice rapidly. Credit: Mike Marosy/NASA."

Caption for second image: "A map of the Southern Ocean’s salinity since 1979 shows a marked decrease – or freshening (shown in blue) – in certain parts of the Ross, Bellingshausen, Amundsen, and Weddell Seas. Modeling studies suggest that this could potentially cause a decrease in water density, which would result in reduced mixing with a deeper and warmer layer of water below, less heat flow upward to the surface, and greater opportunity for sea ice to grow. Increases in salinity are shown in red. Credit: Jinlun Zhang/University of Washington."

Caption for third image: "The weight of accumulated snowfall can press down on a slab of sea ice until it floods with sea water and refreezes to form a layer of “snow-ice.” This image, an estimate of Antarctic snow-ice formation between 1979 and 2001, shows that in September the build-up of snow ice is greatest (indicated by warm colors) along the Eastern Ross Sea and Amundsen Sea. The units are centimeters and reflect increases in ice thickness, not the extent of the ice. Credit: Thorsten Markus/NASA."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 21, 2014, 08:22:27 PM
The linked reference indicates that larger storm-waves induce the Antarctic Sea Ice to break-up earlier in the season than previously considered in model projections for the Antarctic Sea Ice.  As the storminess of the Southern Ocean is increasing with increasing global warming, this implies that the Antarctic Sea Ice Extent should start retreating earlier than previously projected:
A. L. Kohout, M. J. M. Williams, S. M. Dean & M. H. Meylan , (2014), "Storm-induced sea-ice breakup and the implications for ice extent", Nature, Volume: 509, Pages: 604–607, doi:10.1038/nature13262

http://www.nature.com/nature/journal/v509/n7502/full/nature13262.html (http://www.nature.com/nature/journal/v509/n7502/full/nature13262.html)

Abstract: "The propagation of large, storm-generated waves through sea ice has so far not been measured, limiting our understanding of how ocean waves break sea ice. Without improved knowledge of ice breakup, we are unable to understand recent changes, or predict future changes, in Arctic and Antarctic sea ice. Here we show that storm-generated ocean waves propagating through Antarctic sea ice are able to transport enough energy to break sea ice hundreds of kilometres from the ice edge. Our results, which are based on concurrent observations at multiple locations, establish that large waves break sea ice much farther from the ice edge than would be predicted by the commonly assumed exponential decay. We observed the wave height decay to be almost linear for large waves—those with a significant wave height greater than three metres—and to be exponential only for small waves. This implies a more prominent role for large ocean waves in sea-ice breakup and retreat than previously thought. We examine the wider relevance of this by comparing observed Antarctic sea-ice edge positions with changes in modelled significant wave heights for the Southern Ocean between 1997 and 2009, and find that the retreat and expansion of the sea-ice edge correlate with mean significant wave height increases and decreases, respectively. This includes capturing the spatial variability in sea-ice trends found in the Ross and Amundsen–Bellingshausen seas. Climate models fail to capture recent changes in sea ice in both polar regions. Our results suggest that the incorporation of explicit or parameterized interactions between ocean waves and sea ice may resolve this problem."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on June 22, 2014, 01:59:16 AM
Great stuff ASLR.

I think there are good odds for a CT record this year, even though SIA backed down from the highest anomalies during last year’s maximum, and I find it very fascinating to follow the amazing record spree currently ongoing. Antarctic SIA/SIE is of course greatly affected by random noise causing the NISDC to constantly remind their audience about "large interannual variability" whenever presenting SIE numbers from Antarctica. However, form a purely statistical point of view, the current surge in Antarctic sea ice (2012 to present) seems to me increasingly hard to just label as background noise or interannual variability. If these kind of numbers (+1,5M anomaly) continues to tick in, then I would consider it time to start looking for a somewhat more concrete non linear feedback or random multiyear phenomenon which causes Antarctic SIA trends to break from the 1979-2012 trend.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 22, 2014, 06:49:28 PM
Rubikscube,

It is difficult to say what is interannual variability and what is are long-term trends, with such a limited data base, and non-stationary conditions.  Nevertheless, to illustrate your point that since 2012 the NSIDC data for the Antarctic is trending above long-term trend line, I provide the first attached image from NSIDC of the trend line for Antarctic Sea Ice Extent through the end of May 2014, which indeed does illustrate that we are currently well above the long-term trend line.  Furthermore, I provide the second NSIDC image also through the end of May 2014 which shows which specific portions of the Antarctic Sea Ice is trending up and which are trending down.  It is clear to me that the Bellingshausen and Amundsen Sea sector is trending down because of the Tropical Pacific energy being telecommunicated to this sector by the atmosphere; while both the areas near the Weddell and the Ross Seas are trending upwards; which in my opinion is because of the local wind pattern in both of these area is spreading the sea ice out, and forming leads that then freeze to form more ice, and also because both the Weddell and Ross Sea areas have traditionally been areas of large AABW production which is now decreasing, which leaves more cold at the surface of the ocean to freeze the sea ice in both of these areas. 

Certainly stronger local Antarctic winds, and reduced AABW production, is not good news if these factors do largely account for an acceleration of Antarctic Sea Ice Extent growth, as these factors both promote more atmospheric CO2 accumulation over Antarctica, and promote sea level rise contributions from Antarctica.

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on June 25, 2014, 02:53:38 PM
Anomalies currently closing in on all time records and the 2M mark (1,818 million as of the 24th).

It is difficult to say what is interannual variability and what is are long-term trends, with such a limited data base, and non-stationary conditions.

Indeed. Though, what I find perhaps even more indicative of a pattern change than suspiciously many high readings, is the complete lack of low readings (negative anomaly) and even an absence of moderately high readings (0 to +0,5M anomalies). This doesn’t show up in the monthly plots and is best illustrated with a plot such as the one attached. I have a feeling this might be an effect which is created by an atmospheric, or perhaps oceanic, pattern/feature that previously spawned occasionally or seasonally, but after 2011 for some reason turned into a permanent or semi-permanent feature (such as the particular atmospheric feature causing the ongoing Californian drought). That could explain why it apparently has taken 3 years for the anomalies to steadily build to record levels, and it could perhaps also help explain the apparent increase in CO2 venting as you mentioned.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: crandles on June 25, 2014, 05:04:18 PM
1.818 is second highest anomaly after
2007.9672   1.8403077   8.4898138   6.6495061

Regarding possible trend
Average anomaly for 3 month periods:

2010 Q1   0.11911
2010 Q2   0.60992
2010 Q3   0.75691
2010 Q4   0.22015
2011 Q1   0.2347
2011 Q2   0.32435
2011 Q3   0.25924
2011 Q4   0.22286
2012 Q1   0.29032
2012 Q2   0.33977
2012 Q3   0.57323
2012 Q4   0.46164
2013 Q1   0.70349
2013 Q2   0.79582
2013 Q3   0.89601
2013 Q4   1.12115
2014 Q1   0.87486
2014 Q2   1.38021 (is likely to be a little higher as quarter not quite complete yet)

Of 17 chances to rise or fall only 5 were falls. Or if you start with 2011 Q4 only 2 of 10 changes were falls. Even if a 12:5 or 8:2 split looks significantly unlikely, this is likely to be just cherry picking the start date.

If the next 4 quarters are each higher than the last, then I might be more convinced. It is quite possible that there is more sophisticated analysis that might be convincing earlier than this but unless there is an explanation for the start date, I doubt any analysis is going to be convincing yet.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 26, 2014, 12:39:20 AM
Rubikscube,

While I tend to agree with crandle that with the data available we cannot yet identify a change in the Antarctic Sea Ice Extent trend since 2011; nevertheless, I provide the following linked reference (with a free pdf) and the associated image indicating that the Mt Pinatubo super volcanic eruption (in 1991) could have been masking the true trend of Antarctic Sea Ice Extent expansion until 2011; where-after the Antarctic Sea Ice extent contraction associate with Pinatubo could have dissipated, allowing the true trend line to express itself:

Zanchettin, D., Bothe, O., Timmreck, C., Bader, J., Beitsch, A., Graf, H.-F., Notz, D., and Jungclaus, J. H.: Inter-hemispheric asymmetry in the sea-ice response to volcanic forcing simulated by MPI-ESM (COSMOS-Mill), Earth Syst. Dynam., 5, 223-242, doi:10.5194/esd-5-223-2014, 2014

http://www.earth-syst-dynam.net/5/223/2014/esd-5-223-2014.pdf (http://www.earth-syst-dynam.net/5/223/2014/esd-5-223-2014.pdf)

"Abstract. The decadal evolution of Arctic and Antarctic sea ice following strong volcanic eruptions is investigated in four climate simulation ensembles performed with the COSMOS-Mill version of the Max Planck Institute Earth System Model. The ensembles differ in the magnitude of the imposed volcanic perturbations, with sizes representative of historical tropical eruptions (1991 Pinatubo and 1815 Tambora) and of tropical and extra-tropical "supervolcano" eruptions. A post-eruption Arctic sea-ice expansion is robustly detected in all ensembles, while Antarctic sea ice responds only to supervolcano eruptions, undergoing an initial short-lived expansion and a subsequent prolonged contraction phase. Strong volcanic forcing therefore emerges as a potential source of inter-hemispheric interannual-to-decadal climate variability, although the inter-hemispheric signature is weak in the case of eruptions comparable to historical eruptions. The post-eruption inter-hemispheric decadal asymmetry in sea ice is interpreted as a consequence mainly of the different exposure of Arctic and Antarctic regional climates to induced meridional heat transport changes and of dominating local feedbacks that set in within the Antarctic region. Supervolcano experiments help to clarify differences in simulated hemispheric internal dynamics related to imposed negative net radiative imbalances, including the relative importance of the thermal and dynamical components of the sea-ice response. Supervolcano experiments could therefore serve the assessment of climate models' behavior under strong external forcing conditions and, consequently, favor advancements in our understanding of simulated sea-ice dynamics."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on June 26, 2014, 04:12:23 PM
Well, I'm not so sure if there is a new long term trend to be found, for that to happen I would agree that more data is needed. Also, I think the amount of random noise, and perhaps seasonal noise, may be too big in order to properly confirm a new trend with your method. Either way, what I’m claiming is that the 1979-2008 linear trend, with its range of uncertainty, seems to me to be starting lose its predictive value, and symptoms of that include the 30 month streak without daily readings below normal. This might be because of an atmospheric or oceanic AGW feedback, or it might just be a multiyear oscillation (dragon king?) not previously detected because of a limited data range. What comes next, and thus what new trend one can use to predict/describe future SIA which could possibly be better that the decadal trends currently used, is very hard to tell without knowing more specifically what causes the current surge in Antarctic SIA, thus I ask you guys whether or not a more specific cause can be found. For the moment I can accept and agree with your skepticism, but if the anomaly goes beyond 2M and/or the current lack of low readings continue I would start to consider it somewhat ignorant to just blame it on interannual variability.

Very interesting model results BTW.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 26, 2014, 07:36:55 PM
Another possible factor regarding a possible recent increase in Antarctic Sea Ice is that I understand that according to Michael Mann the AMO is in the process of switching from a cool phase to a warm phase (which might be contributing to an expansion of the Weddell Sea sea ice)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: crandles on June 29, 2014, 12:45:04 PM
CT Area +2m anomaly broken:

 2014.4740   1.8176315  12.9782791  11.1606474
 2014.4767   1.7694607  13.0165310  11.2470703
 2014.4795   1.8265678  13.1559267  11.3293591
 2014.4822   1.9341475  13.3419437  11.4077959
 2014.4850   2.0735106  13.5679169  11.4944057

previous record late 2007:

2007.9672   1.8403077   8.4898138   6.6495061

2014 must be record highest for the day on at least 120 of the 177 days so far.
http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html (http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on June 29, 2014, 01:00:25 PM
Impressive. How can we not get a new record maximum this year?
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Lord M Vader on June 29, 2014, 08:36:09 PM
Very impressive to see the threshold of +2 Mn anomaly brake!! Will be very interesting to see if Antarctica will pass the magically 20 Mn km2 per AMSR numbers...

//LMV
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: steve s on June 29, 2014, 09:44:32 PM
Am I accurate if I interpret these numbers as indicating a massive increase in fresh water draining from the continent this year as compared with previous ones? Else I suspect there would have to be a major increase in an available heat sink, and that seems far less likely.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 29, 2014, 10:42:03 PM
steve s,

Certainly, increased fresh water from ice mass loss is likely to be one of the factors contributing to the increased Antarctic Sea Ice Extent; however, other plausible contributing factors include:
(a) the AMO switching to a warming phase; (b) the decreasing production of AABW carrying less cold into the deep ocean (leaving more cold from freezing sea ice); (c) the end of the Mt Pinatubo influence on the Antarctic Sea Ice Extent; and (d) the combined influence of GHGs and the Antarctic ozone hole on the circumpolar westerly wind velocities.

Edit: I note that the precipitation into the Southern Ocean is steadily increasing, so this is also helping to freshen the surface water in the Southern Ocean.

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on June 30, 2014, 05:25:14 AM
The linked reference (with a free access pdf) by Zhang (2014), clearly indicates that the intensification of the westerly winds over the Southern Ocean has contributed significantly to the increase in Antarctic Sea Ice Volumes (see also the attached image):

Zhang, Jinlun, (2014) "Modeling the Impact of Wind Intensification on Antarctic Sea Ice Volume", J. Climate, 27, 202–214; doi: http://dx.doi.org/10.1175/JCLI-D-12-00139.1 (http://dx.doi.org/10.1175/JCLI-D-12-00139.1)

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00139.1 (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00139.1)

Abstract: "A global sea ice–ocean model is used to examine the impact of wind intensification on Antarctic sea ice volume. Based on the NCEP–NCAR reanalysis data, there are increases in surface wind speed (0.13% yr−1) and convergence (0.66% yr−1) over the ice-covered areas of the Southern Ocean during the period 1979–2010. Driven by the intensifying winds, the model simulates an increase in sea ice speed, convergence, and shear deformation rate, which produces an increase in ridge ice production in the Southern Ocean (1.1% yr−1). The increased ridged ice production is mostly in the Weddell, Bellingshausen, Amundsen, and Ross Seas where an increase in wind convergence dominates. The increase in ridging production contributes to an increase in the volume of thick ice (thickness > 2 m) in the Southern Ocean, while the volumes of thin ice (thickness ≤ 1 m) and medium thick ice (1 m < thickness ≤ 2 m) remain unchanged over the period 1979–2010. The increase in thick ice leads to an increase in ice volume in the Southern Ocean, particularly in the southern Weddell Sea where a significant increase in ice concentration is observed. The simulated increase in either the thick ice volume (0.91% yr−1) or total ice volume (0.46% yr−1) is significantly greater than other ice parameters (simulated or observed) such as ice extent (0.14–0.21% yr−1) or ice area fraction (0.24%–0.28% yr−1), suggesting that ice volume is a potentially strong measure of change."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Stephen on July 20, 2014, 12:21:22 PM
So, what's going on here? Yeah, I know it's a "return to mean", but Gee Whiz!  :o

What a Return to Mean!

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fs1.bild.me%2Fbilder%2F260513%2F3103879antarctic.png&hash=f17248c1c2ee6ce8dcaa882d88011c2d) (http://www.bild.me)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on July 20, 2014, 04:52:15 PM
Stephen,

You might want to look at the following thread from Reply #23 down:

http://forum.arctic-sea-ice.net/index.php/topic,622.0.html#lastPost (http://forum.arctic-sea-ice.net/index.php/topic,622.0.html#lastPost)

In that thread I cite the possibility that this is likely related to a parallel drop in the IOD into the negative range, and possibly partially related to a positive swing in the AAO.

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on July 20, 2014, 05:32:50 PM
For those interested in further researching the complex issue of Antarctic Sea Ice, I can recommend the following recent publications which discuss both the influence of ice drifting behavior and regional seasonality:

P. Uotila, P.R. Holland, T. Vihma, S.J. Marsland, N. Kimura. (2014) Is realistic Antarctic sea-ice extent in climate models the result of excessive ice drift?. Ocean Modelling 79, 33-42.
Online publication date: 1-Jul-2014.

http://www.sciencedirect.com/science/article/pii/S1463500314000523 (http://www.sciencedirect.com/science/article/pii/S1463500314000523)

Abstract: "For the first time, we compute the sea-ice concentration budget of a fully coupled climate model, the Australian ACCESS model, in order to assess its realism in simulating the autumn–winter evolution of Antarctic sea ice. The sea-ice concentration budget consists of the local change, advection and divergence, and the residual component which represents the net effect of thermodynamics and ridging. Although the model simulates the evolution of sea-ice area reasonably well, its sea-ice concentration budget significantly deviates from the observed one. The modelled sea-ice budget components deviate from observed close to the Antarctic coast, where the modelled ice motion is more convergent, and near the ice edge, where the modelled ice is advected faster than observed due to inconsistencies between ice velocities. In the central ice pack the agreement between the model and observations is better. Based on this, we propose that efforts to simulate the observed Antarctic sea-ice trends should focus on improving the realism of modelled ice drift."

Paul R. Holland. (2014) The seasonality of Antarctic sea ice trends. Geophysical Research Letters, n/a-n/a. Online publication date: 1-Jun-2014.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060172/abstract;jsessionid=2FBF7889EF7E1AE3C35E3467F7698B5D.f03t03 (http://onlinelibrary.wiley.com/doi/10.1002/2014GL060172/abstract;jsessionid=2FBF7889EF7E1AE3C35E3467F7698B5D.f03t03)

Abstract: "Antarctic sea ice is experiencing a weak overall increase in area that is the residual of opposing regional trends. This study considers their seasonal pattern. In addition to traditional ice concentration and total ice area, temporal derivatives of these quantities are investigated (“intensification” and “expansion,” respectively). This is crucial to the attribution of trends, since changes in forcing directly affect ice areal change (rather than ice area). Diverse regional trends all contribute significantly to the overall increase. Trends in the Weddell and Amundsen-Bellingshausen regions compensate in magnitude and seasonality. The largest concentration trends, in autumn, are actually caused by intensification trends during spring. Autumn intensification trends directly oppose autumn concentration trends in most places, seemingly as a result of ice and ocean feedbacks. Springtime trends are reconcilable with wind trends, but further study of changes during the spring melting season is required to unravel the Antarctic sea ice increase."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on July 24, 2014, 06:33:19 PM
Joe Romm provides additional discussion on the true nature of Antarctic sea ice at the following link to a Climate Progress article:

http://thinkprogress.org/climate/2014/07/23/3463124/antarctic-sea-ice-trend/ (http://thinkprogress.org/climate/2014/07/23/3463124/antarctic-sea-ice-trend/)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on September 16, 2014, 09:33:16 PM
Looks like CT area number just smashed through the previous all time record answering the initial question of this thread once and for all. Celebrations are probably well underway in the denialosphere.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: viddaloo on September 17, 2014, 01:15:08 AM
Looks like CT area number just smashed through the previous all time record answering the initial question of this thread once and for all. Celebrations are probably well underway in the denialosphere.

LOL, Rubik! Thanks for the info & warning, tho. I actually think it's good for pedagogic reasons, as many deniers now will learn that we have two polar regions and that there's a difference between the Arctic and Antarctic, although they sound rather similar.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Laurent on September 17, 2014, 08:58:17 AM
May be they will learn to do the difference between winter and summer...
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 17, 2014, 11:08:10 PM
The attached Terra satellite image taken Sept 17 2014, shows that in front the critical Pine Island Glacier there is zero sea ice, making it irrelevant that the sea ice elsewhere in Antarctica may be above average, with regard to contribution to sea level rise.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Laurent on September 18, 2014, 10:47:09 AM
That is very impressive, it is not only pig but the west Antartic and the north east also.
Look at that !
http://1.usa.gov/1uVOROt (http://1.usa.gov/1uVOROt)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 18, 2014, 12:20:04 PM
Laurent,

The pictures you posted leaves me with the impression that upwelling around Antarctic is more active than usual, which, if true, would promote more basal ice melting, more freshening of the ocean water, and consequently more sea ice growth (which could partially explain the record Antarctic sea ice extent).

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 18, 2014, 02:47:32 PM
While the contribution to Antarctic sea ice extent from the freshening of the Southern Ocean is significant (as is local wind velocity), NOAA made the following comment this week:

"We suspect that the increasing presence of icebergs broken off from ice shelves and glaciers within the Antarctic sea ice pack is a major contributor to a temporary but increasing trend in the Antarctic sea ice extent."

This cannot be good news for SLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: nowayout on September 18, 2014, 08:40:48 PM
The (year over year increasing) freshwater layer from calving and meltwater runoff, which builds through the austral summer, helps with the sea ice extend records, as well as the (increasing) local wind velocity shears and breaks the winter ice, the rifts quickly refreezing. All be gone next austral summer. Otoh, basal melting and upwelling destroys the freshwater layer.

No surprise so far.

Is it too early for the melting in front of the shelves to start? I guess it is. Are they different places compared to the other years? (Did some currents shift? Could there be effects from an El Nino that did not come? Not yet.)

Just wondering. This year's record won't hold for long, though.

Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 18, 2014, 11:55:52 PM
The Southern Ocean currently has an increasing trend of heat uptake that can/will increase basal ice melting, and I get the impression that this has been a windy austral winter, that both creates sea ice and can drive ocean currents to accelerate and increase upwelling.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: lanevn on September 22, 2014, 11:32:59 AM
Wow, 16.807, looks like time to correct models into another direction ).
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on September 22, 2014, 02:23:44 PM
Indeed lanevn. The margin of record is currently 0,574, which is slightly less than the "record margin of record" saw in 1980 which was only the second year of measurements.

While the contribution to Antarctic sea ice extent from the freshening of the Southern Ocean is significant (as is local wind velocity), NOAA made the following comment this week:

"We suspect that the increasing presence of icebergs broken off from ice shelves and glaciers within the Antarctic sea ice pack is a major contributor to a temporary but increasing trend in the Antarctic sea ice extent."

This cannot be good news for SLR

I have always struggled to see the connection between increased mass loss and increase in antarctic SIE since most, if not all of the additional mass loss is happening in West-Antarctica while Bellingshausen sea (outside of West Antarctica) apparently is the only austral sea which have seen SIE trends more similar to those in the Arctic. If it was the case though, that icebergs are thrown into the circumpolar currents and thus freshens the top layer of the ocean all over the place, that would in a way make more sense. Is this the theory, or is it simply that we are seeing increased mass loss all over Antarctica, but that this is in most places offset be increased mass gain?
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 22, 2014, 04:43:46 PM
Rubikscube,

First, the decrease in the average Southern Ocean salinity is only one factor associated with the increase in Antarctic Sea Ice Extent (see the discussion at the beginning of this thread, as you well know), and wind patterns (that moves the already formed sea ice laterally so that more sea ice can form) is an even more significant factor, which particularly impacts both the Weddell, and the Ross, Sea regions.

Second, the Bellingshausen Sea area include portions of both the Antarctic Peninsula and also portions of West Antarctica.

Third, if appears that you are confusing ice mass loss from grounded glaciers (which contributes to SLR, and which is dominated by the WAIS) and ice mass loss from floating ice shelves (which does not contribute to SLR, and which occurs all around the perimeter of Antarctica); but both of which reduce the salinity of the Southern Ocean.  Furthermore, it is not only the melting of icebergs and bergy bits that help to distribute fresh water around the Southern Ocean, but more importantly the currents rapidly distribute the fresher water layers around the entire Southern Ocean.

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Sleepy on September 22, 2014, 04:49:04 PM
One might also consider the recovered data from Nimbus 1, regarding Antarctica.
In 63-64 there were a moderate El Nino followed by a weak La Nina 64-65.

Link to the paper: http://www.the-cryosphere.net/7/699/2013/tc-7-699-2013.pdf (http://www.the-cryosphere.net/7/699/2013/tc-7-699-2013.pdf)

Quote from the attached picture.
Fig. 4. Time series of Antarctic September sea ice extent. The Nimbus
I estimate for 1964 is to the left in red as a box and whisker
plot, with the passive microwave NSIDC Sea Ice Index values for
1979–2012 in blue. For Nimbus, the box represents the standard deviation
of the different edge locations, while the whiskers represent
the absolute maximum and minimum range. The blue solid line is
the monthly average passive microwave September values, while
the blue dashed lines represent a three-day average of the high and
low range of daily extents during the month.


Edit; From cires about Nimbus.
http://cires.colorado.edu/news/press/2014/nimbus.html (http://cires.colorado.edu/news/press/2014/nimbus.html)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on September 22, 2014, 06:45:47 PM
Thank you for clarifying ASLR. I might have been neglecting the freshening created by melt from the floating ice shelves :-[
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 23, 2014, 12:50:52 AM
The following linked Internet BBC article indicates that about 80% of the recent (past couple of weeks) increase is mostly located in the Ross Sea area where strong winds associated with the persistent ASL is pushing the sea ice to northerly latitudes so that more ice can form in the associated leads (see quote below).  Also, I would like to note that the ASL generally does not typically start in earnest until October; and furthermore, if an El Nino event gets started in the next few weeks (see the ENSO thread in the Consequences folder), then the extant ASL would likely migrate eastward where it would likely blow more warm CDW into the ASE where it would accelerate grounding line retreat for the marine glaciers there:

http://www.bbc.com/news/science-environment-29312320 (http://www.bbc.com/news/science-environment-29312320)

Quote: "… Prof John Turner, highlighted the big up-turn in sea-ice growth around the Antarctic in only the past fortnight - the result of more storms in the region.

"Southerly winds have pushed the ice out to greater northerly latitudes, and that means the cold winds coming off the continent then freeze the open water left behind."
Principally, this is seen in the Ross Sea area of Antarctica. Indeed, more than 80% of the growth trend is focussed on this one region.

Prof Turner said he thought the persistent behaviour of a low-pressure system known as the Amundsen Sea Low (ASL) was probably at the root of the observed Antarctic trend, but as to why that was the case - no-one could yet explain."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on September 28, 2014, 08:34:04 PM
As a follow-up to my post in Reply #42, I would like to note that per the Australian Bureau of Meteorology (BoM) for the week ending Sept 21, 2014 the Nino 3.4 index moved above +0.5 (indicating El Nino-like conditions), and under El Nino like conditions the ASL migrates eastward where it tends to blow warm CDW into the ASE as indicated in the attached earth surface wind maps for Sept 26 & 28 2014, respectively: 
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on October 09, 2014, 08:57:34 PM
I would also like to note that while the Antarctic sea ice area did hit a record peak during Sept 2014 (when the albedo does not influence global warming much); as the attached image from Cryosphere Today indicates the Antarctic sea ice area is now well below the 2013 sea ice extent, at this time of year (October); and I expect much more Antarctic sea ice area loss before December when the Antarctic sunshine peaks.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: wili on October 13, 2014, 07:44:08 PM
Expanding Antarctic Sea Ice = ‘Warning Bell’

http://www.climatecentral.org/news/antarctica-ice-melt-sea-level-18155 (http://www.climatecentral.org/news/antarctica-ice-melt-sea-level-18155)

Quote
“We found out that if you put a certain amount of freshwater into the Southern Ocean around Antarctica, then basically it reduces this overturning — it reduces the upwelling of that warm water,” said the study’s lead author, Nick Golledge, a scientist at the Victoria University of Wellington’s Antarctic Research Center in New Zealand.

“All that heat just gets trapped at a depth where it can melt the base of the ice shelves and the grounded ice that’s sitting in the ocean.
Title: Re: Will Antarctica sea ice set a new record in 2014? Yes but where now?
Post by: crandles on November 18, 2014, 12:52:36 AM
2014.8712   0.2693349  12.7672272  12.4978924

Positive anomaly of 0.269 is lowest anomaly for over 2 years.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Farctic.atmos.uiuc.edu%2Fcryosphere%2FIMAGES%2Fseaice.anomaly.antarctic.png&hash=bcebfa7dcdb1e2301dd130c4a85e39eb)

That strong upward movement of last 3 years now broken? If so, why? Or is it just random movements?
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on November 18, 2014, 02:09:44 AM
crandles,

According to the linked article (in press) a slow response mechanism from the Antarctic ozone hole formation (some three decades ago) should now be strong enough to start returning the extent of the Antarctic sea ice extent (particularly in the austral summer). The reference (with an open access pdf) indicates that two coupled climate models show that in response to an ozone depletion the Southern Ocean responded with two processes for sea ice extent change.  The first process based on a northward Ekman drift occurred relatively quickly and served to expand Antarctic sea ice extent about three decades ago.  The second process acted relatively more slowly (years to decades), results in a warming trend for the Southern Ocean leading to a reduction in projected sea ice extent (see attached figure).  Based on these findings we can expect Antarctic amplification to begin accelerating in the next decade or so.

David Ferreira, John Marshall, Cecilia M. Bitz, Susan Solomon, and Alan Plumb, (2014) "Antarctic ocean and sea ice response to ozone depletion: a two timescale problem", Journal of Climate, In press.

http://www.met.rdg.ac.uk/~gf905417/Publications_files/Twotimescale_final.pdf (http://www.met.rdg.ac.uk/~gf905417/Publications_files/Twotimescale_final.pdf)


Abstract: "The response of the Southern Ocean to a repeating seasonal cycle of ozone loss is studied in two coupled climate models and found to comprise both fast and slow processes. The fast response is similar to the inter-annual signature of the Southern Annular Mode (SAM) on Sea Surface Temperature (SST), on to which the ozone-hole forcing projects in the summer. It comprises enhanced northward Ekman drift inducing negative summertime SST anomalies around Antarctica, earlier sea ice freeze-up the following winter, and northward expansion of the sea ice edge year-round. The enhanced northward Ekman drift, however, results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice. With sustained bursts of westerly winds induced by ozone-hole depletion, this warming from below eventually dominates over the cooling from anomalous Ekman drift. The resulting slow-timescale response (years to decades) leads to warming of SSTs around Antarctica and ultimately a reduction in sea-ice cover year-round. This two-timescale behavior – rapid cooling followed by slow but persistent warming - is found in the two coupled models analysed, one with an idealized geometry, the other a complex global climate model with realistic geometry. Processes that control the timescale of the transition from cooling to warming, and their uncertainties are described. Finally we discuss the implications of our results for rationalizing previous studies of the effect of the ozone-hole on SST and sea-ice extent."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: sidd on November 18, 2014, 07:55:04 AM
Re: Golledge(2014) doi:10.1038/ncomms610 on suppression of heat loss from upwelling water in the southern ocean due to freshwater cap from ice melt, as in MWP1A

Look also at Weber(2014) doi:10.1038/nature13397 on timing of icerafted antarctic debris
 
and to put in historical (last 5 stades) context Grant(2014) doi:10.1038/ncomms6076

That said, i fear that we are outside Pleistocene (post glacial cycle onset) paleo evidence. Pliocene (just b4 Pleistocene) might be a better analog.

But what do i know. i'm just a sometime fizicist. Talk to the geologists on that one. The ones i know don't deny the possibility. That don't mean they support it either ...

sidd
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: crandles on November 18, 2014, 02:33:47 PM
crandles,

According to the linked article (in press) a slow response mechanism from the Antarctic ozone hole formation (some three decades ago) should now be strong enough to start returning the extent of the Antarctic sea ice extent (particularly in the austral summer). The reference (with an open access pdf) indicates that two coupled climate models show that in response to an ozone depletion the Southern Ocean responded with two processes for sea ice extent change.  The first process based on a northward Ekman drift occurred relatively quickly and served to expand Antarctic sea ice extent about three decades ago.  The second process acted relatively more slowly (years to decades), results in a warming trend for the Southern Ocean leading to a reduction in projected sea ice extent (see attached figure).

The ice levels after 1987 do seem higher than before which seems some support for that first process.

Not sure I see support for the second process in the data. CCSM shows a rapid fall just 6 years later. MIT shows 6-8 years of slow gains before remaining flat for 8-10 years before losses dominate. The data seems to show slow gains for ~30 years.

Would you expect something different from what the models show? Could a slow increase in CDW thinning the ice lead to thin ice being blown further north allowing more thin ice production for a longer period like nearly 30 years? After sufficient thinning would there eventually be a point where the ice melts more rapidly than the increasing northward ice movement can compensate for? Would you expect a more rapid decline after this longer delay before the decline starts?

Is that stretching the model results too far in order to try to fit the data?


Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on November 18, 2014, 03:53:10 PM
crandles,

I do not have time for a long post; however, in his post just before your post, sidd points out that there are other positive feedback mechanisms for Antarctic sea ice growth that the Ferreira et al 2014 models did not capture.  If you are looking for model projection that very closely match all aspects of the observed record, you will need to wait at least ten years for the ACME projection to be available, and you should hope that that Earth System Model had enough money to include the two feedback mechanisms that Ferreirra et al 2014 identified, together with the thousands of other feedback systems affecting the projections (or hindcasts).

Best,
ASLR
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Sleepy on November 19, 2014, 07:33:38 AM
One thing that I didn't comment in Reply #40 regarding the recovered Nimbus data from the sixties, is that following the record high sea ice extent in -64 with the La Nina, there was a record low two years later after the following El Nino.

Even with those measured mass changes in the glaciers lately and the increase in maximum sea ice extent, I think it is entirely possible to see a dramatic drop in 2015 or -16.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on November 25, 2014, 12:33:40 AM
The linked reference shows that the Antarctic sea ice is getting thicker in some areas possibly due to increased rafting of the ice (possibly due to stronger winds and storms, due to climate change):

G. Williams, T. Maksym, J. Wilkinson, C. Kunz, C. Murphy, P. Kimball & H. Singh, (2014), "Thick and deformed Antarctic sea ice mapped with autonomous underwater vehicles", Nature Geoscience, doi:10.1038/ngeo2299

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2299.html (http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2299.html)

Abstract: "Satellites have documented trends in Antarctic sea-ice extent and its variability for decades, but estimating sea-ice thickness in the Antarctic from remote sensing data remains challenging. In situ observations needed for validation of remote sensing data and sea-ice models are limited; most have been restricted to a few point measurements on selected ice floes, or to visual shipboard estimates. Here we present three-dimensional (3D) floe-scale maps of sea-ice draft for ten floes, compiled from two springtime expeditions by an autonomous underwater vehicle to the near-coastal regions of the Weddell, Bellingshausen, and Wilkes Land sectors of Antarctica. Mean drafts range from 1.4 to 5.5 m, with maxima up to 16 m. We also find that, on average, 76% of the ice volume is deformed ice. Our surveys indicate that the floes are much thicker and more deformed than reported by most drilling and ship-based measurements of Antarctic sea ice. We suggest that thick ice in the near-coastal and interior pack may be under-represented in existing in situ assessments of Antarctic sea ice and hence, on average, Antarctic sea ice may be thicker than previously thought."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on February 11, 2015, 10:51:40 PM
This post is provided to bump this thread, and to provide a link to the final published version of the reference provided in Reply #47, indicating that we can expect Antarctic Amplification to start increasing in a decade or two:

David Ferreira, John Marshall, Cecilia M. Bitz, Susan Solomon, and Alan Plumb, 2015: "Antarctic Ocean and Sea Ice Response to Ozone Depletion: A Two-Time-Scale Problem". J. Climate, 28, 1206–1226, doi: http://dx.doi.org/10.1175/JCLI-D-14-00313.1 (http://dx.doi.org/10.1175/JCLI-D-14-00313.1)

http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00313.1 (http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00313.1)

Abstract: "The response of the Southern Ocean to a repeating seasonal cycle of ozone loss is studied in two coupled climate models and is found to comprise both fast and slow processes. The fast response is similar to the interannual signature of the southern annular mode (SAM) on sea surface temperature (SST), onto which the ozone hole forcing projects in the summer. It comprises enhanced northward Ekman drift, inducing negative summertime SST anomalies around Antarctica, earlier sea ice freeze-up the following winter, and northward expansion of the sea ice edge year-round. The enhanced northward Ekman drift, however, results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice. With sustained bursts of westerly winds induced by ozone hole depletion, this warming from below eventually dominates over the cooling from anomalous Ekman drift. The resulting slow time-scale response (years to decades) leads to warming of SSTs around Antarctica and ultimately a reduction in sea ice cover year-round. This two-time-scale behavior—rapid cooling followed by slow but persistent warming—is found in the two coupled models analyzed: one with an idealized geometry and the other with a complex global climate model with realistic geometry. Processes that control the time scale of the transition from cooling to warming and their uncertainties are described. Finally the implications of these results are discussed for rationalizing previous studies of the effect of the ozone hole on SST and sea ice extent."
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on March 02, 2015, 11:42:06 AM
I would like to point-out that most of the increase in the Antarctic sea ice extent is occurring in the Weddell Sea Sector, where the linked article points to research indicating that such sea ice can (and has in the past) reduced the Southern Hemispheric upwelling of the AMOC; which results in the re-direction of this warm ocean water to promote the melting of adjoining glacial ice (with probable serious consequences for the potential early collapse of the FRIS).

http://www.huffingtonpost.com/2014/10/13/antarctic-sea-ice_n_5978238.html?cps=gravity_2845_-3174118750263476582 (http://www.huffingtonpost.com/2014/10/13/antarctic-sea-ice_n_5978238.html?cps=gravity_2845_-3174118750263476582)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Jim Hunt on March 02, 2015, 12:16:58 PM
I would like to point-out that most of the increase in the Antarctic sea ice extent is occurring in the Weddell Sea Sector

See the shiny new (and still not quite fully automated) regional Antarctic sea ice area/extent plots at:

http://GreatWhiteCon.info/resources/antarctic-sea-ice-graphs/ (http://GreatWhiteCon.info/resources/antarctic-sea-ice-graphs/)

By way of example:

Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: AbruptSLR on March 02, 2015, 04:13:41 PM
While there are different ways to group and categorize Antarctic Sea Ice extent/area, the attached NSIDC daily sea ice extent map for March 1 2015 clearly shows the Indian Ocean and Pacific Ocean, sea ice sectors below average (for this time of year) while the Weddell Sea Sector is clearly above average.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on March 04, 2015, 03:09:54 AM
Thank you Jim. A regional breakdown of Antarctic SIA/SIE is something I have been missing.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Jim Hunt on March 04, 2015, 12:04:00 PM
Thank you Jim. A regional breakdown of Antarctic SIA/SIE is something I have been missing.

My pleasure! Don't forget to thank Wipneus also, whose Raspberry Pi does the number crunching.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Rubikscube on April 01, 2015, 02:21:51 AM
The two attachments posted below display the average sea ice concentration at maximum for the period of 2002-2013 and furthermore how the record breaking maximum in 2014 compared to this average. Notice amongst other things how abnormally large the coastal polynyas were in 2014.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Kuni on June 01, 2015, 09:48:26 PM
Antarctic sea ice is not relevant because unlike the Arctic, which is 100% sea ice, the Antarctic ice pack is overwhelmingly non-sea ice.

The Antarctic ice pack should only be tracked in its entirety and the fact hammered home that the increase in Antarctic sea ice, unlike increased Arctic sea ice, is very very bad because it should not have fallen off the continent into the sea to begin with.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Paddy on June 03, 2015, 12:37:09 PM
It's not that simple.  Most of it hasn't just "fallen off the continent"; instead it's been formed out out at sea.  Lots of theories as to why it's forming over a larger area and extent now, but I'm not sure what the leading theories are. 

However, this is happening at a time of net loss of ice mass on the Antarctic continent, according to GRACE data, so it's pretty clearly not that ice is increasing across Antarctica and the surrounding area overall.  Also, it's happening at a time of net loss of ice over the entire rest of the planet, so it's unsurprising that "sceptics" have a tendency to overemphasise its importance.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Chuck Yokota on June 03, 2015, 02:42:23 PM
Also, the increase has been happening during a period of time when the water and air temperature have both been getting warmer, so it is clear that other factors, perhaps surface salinity or the way the ice spreads out, are the cause. Antarctic ice expanding is probably just as much a result of global warming as Arctic ice decreasing, but it just runs counter to our intuition.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: plinius on June 03, 2015, 02:57:22 PM
I always like to compare quantities. Total ice mass loss (shelf + land ice) in antarctica is easily >300 Gt per year. If you spread that out in a 1m thick layer, you get about 0.3 Mio square kilometers. If you use the typical turnover time of ~ 6 years for the most concerned regions of the sea ice increase (i.e. Weddel/Ross), you would estimate a sea ice area increase of ~2 Mio sqkm alone from that source. So no, I cannot see what would run counter to my intuition. It is, if I do not get other information, just a continent shedding its ice cap...
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Chuck Yokota on June 03, 2015, 10:33:20 PM
plinius- The non-landfast sea ice nearly all melts every summer and refreezes every winter. There is no real carryover from year to year. Also, the sea ice is in the shape of flat ice floes, icebergs calved from glaciers are very thick and irregular.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Michael Hauber on June 04, 2015, 05:11:46 AM
Also, the increase has been happening during a period of time when the water and air temperature have both been getting warmer,

Are you sure?  GISS trends  (http://data.giss.nasa.gov/gistemp/maps/) suggest that the ocean around Antarctica has been getting cooler since 1980, which is the period we've measured the increase in Antarctic sea ice.  Trends for land based stations are positive, but amongst the weakest for the entire globe (look at the zonal mean by latitude down the bottom after making a map)

It seems likely that the tightening and intensification of the polar vortex over Antarctica is a significant factor.   First this speeds up the current around Antarctica.  Speeding up these currents will result in more water moving past the bottom of the ice sheets, so more melting from below, even if the water is not warming up.  At the same time the insulation of Antarctica from the rest of the globe is increased, so Antarctica cools down relative to the rest of the world.  As Antarctica has still warmed since 1980 this effect may only be weak enough to offset part of this warming.   Thirdly the current flings ice and cold water north faster, so the area of ice and coldest surface waters expands.  Fourthly as this water meets against currents in the adjacent oceans this drives intensified downwelling in the Antarctic Convergence (http://en.wikipedia.org/wiki/Antarctic_Convergence) zone.  This intensified downwelling then increases the transport of heat into the deeper parts of the southern ocean.

The intensification of the Antarctic vortex has been blamed largely on the Ozone hole, although I think I've seen at least one or two speculations that AGW may also contribute.  There may also be a role for natural variability.  It is interesting to note that while the warming trends from 1980 to 2012 around Antarctica are weak or non-existent, the trends from early dates to now are much stronger, so there may be a multi-decade variation relating to something like AMO or PDO.  I've seen hints that there may have been much more Antarctic sea ice prior to the current satellite record since 1980, with the Nimubs satellite (http://www.bbc.com/news/science-environment-22271972) revealing higher sea ice in 1964, and whaling records (http://www.nature.com/nature/journal/v389/n6646/full/389057a0.html) for earlier years also hinting at an ice edge further north.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Sleepy on June 04, 2015, 05:41:50 AM
Regarding my comments above in #40 & #51 around the recovered Nimbus missions, I'll quote the cires article in #40 to highlight what I personally think is the thing to look for within a couple of years. A record low.
Quote
“And the Antarctic blew us away,” he said. In 1964, sea ice extent in the Antarctic was the largest ever recorded, according to Nimbus image analysis. Two years later, there was a record low for sea ice in the Antarctic, and in 1969 Nimbus imagery, sea ice appears to have reached its maximum extent earliest on record.

Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Yuha on June 04, 2015, 11:48:58 AM
NSIDC monthly Arctic Sea Ice News & Analysis for May has a section on Antarctic sea ice too.

http://nsidc.org/arcticseaicenews/2015/06/may-be-declining/ (http://nsidc.org/arcticseaicenews/2015/06/may-be-declining/)

Quote
Despite the record sea ice extent, air temperatures at the 925 millibar level (about 3,000 feet above the surface) remained generally above average for most of the continent and coastal areas of the surrounding ocean. Air temperatures were as much as 5 degrees Celsius (9 degrees Fahrenheit) above the 1981 to 2010 average over the West Antarctic ice sheet and central Ross Sea. The region of high ice extent near the northeastern Ross Sea had near-average air temperatures in the vicinity of the ice edge. Cooler than average temperatures were observed near the ice edge in the northeastern Weddell Sea (2 degrees Celsius, or 4 degrees Fahrenheit, below average) and Davis Sea (4 degrees Celsius, or 7 degrees Fahrenheit, below average).
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: plinius on June 04, 2015, 01:13:53 PM
plinius- The non-landfast sea ice nearly all melts every summer and refreezes every winter. There is no real carryover from year to year. Also, the sea ice is in the shape of flat ice floes, icebergs calved from glaciers are very thick and irregular.

Well, shape does not matter. You melt the glaciers/icebergs, contribute to the cold, sweet surface layer that refreezes into your favourite sea ice shape. Second, I haven't heard that nearly all antarctic sea ice melts out nowadays, 2.5 Mio sqkm remains through summer, mostly in the Weddel/Ross seas, where the water cycle is longest. Certainly not saying that this is the only reason, but it will contribute and also push the ice edge out.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Sleepy on July 27, 2015, 08:13:21 AM
Almost back to 1979-2008 mean now.

http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.antarctic.png (http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.antarctic.png)
http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html (http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html)
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Gray-Wolf on July 27, 2015, 01:29:39 PM
Seems like we'll all have a quiet summer ? No constant denier whine about  Antarctic Sea ice levels?

I was wondering if the nino would mess with storm tracks around Antarctica this southern winter and it appears they are ( hence the Ozzy snow)?

The nasty side arrives over the summer in Antarctica. We know that La Nina slows losses from Thwaites/P.I.G. due to wind forcings so will Nino bring the opposite? The warm water is already in place so a forcing that keeps throwing it at the ice cliffs is not good.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Jim Hunt on July 27, 2015, 07:00:28 PM
Seems like we'll all have a quiet summer ? No constant denier whine about  Antarctic Sea ice levels?

No such luck! I felt compelled to inform a whining denier at The Telegraph about the Antarctic sea ice "kink"  only yesterday:

https://disqus.com/home/discussion/telegraphuk/how_arctic_ice_has_made_fools_of_all_those_poor_warmists/#comment-2158010638

Of course up above that Booker was talking ballcocks about the Arctic also.
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: wehappyfew on July 28, 2015, 02:16:57 AM
It looks like Austral summer will be exciting around the edge of the sea ice, maybe due to El Nino warmth spreading south?

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.cpc.ncep.noaa.gov%2Fproducts%2Fpeople%2Fwwang%2Fcfsv2fcst%2FimagesInd3%2FglbT2mMonInd6.gif&hash=9b011d25d6dd913a8a084c8bd08610b4)

Record low ice extent for Antarctica?
Title: Re: Will Antarctica sea ice set a new record in 2014?
Post by: Lennart van der Linde on July 28, 2015, 09:45:36 AM
Chris Mooney on Hansen et al and its implications for growing Antarctic sea ice extent:
http://www.washingtonpost.com/news/energy-environment/wp/2015/07/27/climate-change-skeptics-may-be-about-to-lose-one-of-their-favorite-arguments/?postshare=1821438025395214 (http://www.washingtonpost.com/news/energy-environment/wp/2015/07/27/climate-change-skeptics-may-be-about-to-lose-one-of-their-favorite-arguments/?postshare=1821438025395214)

"There’s no doubt that growing Antarctic sea ice is a mystery in the climate system — and an anomalous, seemingly contrary indicator. However, if a controversial and much-discussed new paper from famed former NASA scientist James Hansen and 16 colleagues is correct, then actually it could be a troubling climate warning sign. (Indeed, other scientists have reached similar conclusions.)

According to Hansen’s thinking, expanding Antarctic sea ice is precisely what you would expect to see if the Antarctic continent itself is losing a lot of ice mass from its vast ice sheet, adding to sea level rise.

The thinking goes like this: As ice shelves melt, and more inland ice slides towards the sea, a gigantic volume of cold, fresh water enters the ocean. This freshwater pulse, the researchers continue, promotes ocean “stratification,” in which a cold surface layer lies atop a subsurface warmer layer. The cold surface layer promotes more sea ice growth atop open water, while the warm lower layer sneaks beneath that ice and continues to melt submerged ice shelves, which plunge deep into the water at the fringes of the continent.

The fundamental physical reason for the expansion of sea ice in this scenario is that cold, fresh water is less dense than warmer, salty water. Or as the National Snow and Ice Data Center explains:

As deep ocean temperatures around Antarctic rise, they increase ice shelf melt, according to a study led by Richard Bintanja. This meltwater is creating a cool layer near the surface of the ocean that promotes sea ice production. In addition, the meltwater is fresh, or much less salty and dense than surrounding saline ocean layers. So fresher meltwater floats upward, mixing with the cold surface layer, lowering its density. As this fresh layer expands, it forms a stable puddle on top of the ocean that makes it easier to produce and retain sea ice.

In this sense, expanding Antarctic sea ice might be anything but good news.

Indeed, in the troubling scenario outlined by Hansen and his colleagues, it’s part of a series of feedbacks that lead to rapid sea level rise. “Amplifying feedbacks, including slowdown of [the Southern ocean’s overturning circulation] and cooling of the near-Antarctic ocean surface with increasing sea ice, may spur nonlinear growth of Antarctic ice sheet mass loss,” write Hansen and his colleagues.

“Effects of freshwater injection and resulting ocean stratification are occurring sooner in the real world than in our model,” they add.

Reached by phone, Hansen added that one reason he thinks the model he is using is is right — and other models are not — is that it captures Antarctic sea ice expansion. “All the other models have sea ice disappearing as the planet get warmer,” he says. He also thinks the Antarctic ice expansion trend will continue, along with ice sheet melt.

“It will be clearer, give us a few more years,” he says...

It’s also worth noting that other explanations for the expansion of Antarctic sea ice have been offered that do not turn on meltwater and ocean freshening. Overall, it’s not clear that scientists yet fully understand what’s going on in this extremely remote part of the climate system.

Nonetheless, this serves to point out the danger of seizing on a mysterious anomaly in the climate system — like expanding Antarctic sea ice — and interpreting it to score political points. For what may seem like good news for the climate — and bad news for climate “alarmists,” as skeptics put it — could be the utter opposite."