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Author Topic: Trends for the Southern Ocean  (Read 41259 times)

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #50 on: September 18, 2013, 06:20:59 PM »
The linked reference indicates that the intensifying regional winds in Antarctic is one of the more significant factors accounting for the increasing maximum extent of Antarctic sea ice.  As the increasing intensity of these regional Antarctic winds can lead to in increased amount of cross-shelf warm CDW transport, this is now good news for the future stability of the WAIS and for the coastal areas of the EAIS:

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

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."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #51 on: September 18, 2013, 10:56:22 PM »
The following links lead to articles about recent research about the use of an algorithm to indentify more phytoplankton in the Southern Ocean that previously identified; which might be good for more CO2 sequestration (depending on the size of the phytoplankton and their tendency to sink, or not):

http://phys.org/news/2013-09-algorithm-phytoplankton-southern-ocean.html

http://www.sciencedaily.com/releases/2013/09/130918102004.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+(ScienceDaily%3A+Latest+Science+News)

The following is the link to the reference discussed above:

http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20270/abstract


Johnson, R., P. G. Strutton, S. W. Wright, A. McMinn, and K. M. Meiners (2013), Three improved Satellite Chlorophyll algorithms for the Southern Ocean, J. Geophys. Res. Oceans, 118, 3694–3703, doi:10.1002/jgrc.20270.


Abstract:
"Remote sensing of Southern Ocean chlorophyll concentrations is the most effective way to detect large-scale changes in phytoplankton biomass driven by seasonality and climate change. However, the current algorithms for the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, algorithm OC4v6), the Moderate Resolution Imaging Spectroradiometer (MODIS-Aqua, algorithm OC3M), and GlobColour significantly underestimate chlorophyll concentrations at high latitudes. Here, we use a long-term data set from the Southern Ocean (20°–160°E) to develop more accurate algorithms for all three of these products in southern high-latitude regions. These new algorithms improve in situ versus satellite chlorophyll coefficients of determination (r2) from 0.27 to 0.46, 0.26 to 0.51, and 0.25 to 0.27, for OC4v6, OC3M, and GlobColour, respectively, while addressing the underestimation problem. This study also revealed that pigment composition, which reflects species composition and physiology, is key to understanding the reasons for satellite chlorophyll underestimation in this region. These significantly improved algorithms will permit more accurate estimates of standing stocks and more sensitive detection of spatial and temporal changes in those stocks, with consequences for derived products such as primary production and carbon cycling."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #52 on: September 18, 2013, 11:32:59 PM »
The following linked reference cited physical measurement of the distribution of microbial assemblages in the Southern Ocean:

Advection shapes Southern Ocean microbial assemblages independent of distance and environment effects; by: David Wilkins, Erik van Sebille, Stephen R. Rintoul, Federico M. Lauro & Ricardo Cavicchioli; Nature Communications; 4, Article number: 2457; doi:10.1038/ncomms3457; 16 September 2013

http://www.nature.com/ncomms/2013/130916/ncomms3457/abs/ncomms3457.html


Abstract:
"Although environmental selection and spatial separation have been shown to shape the distribution and abundance of marine microorganisms, the effects of advection (physical transport) have not been directly tested. Here we examine 25 samples covering all major water masses of the Southern Ocean to determine the effects of advection on microbial biogeography. Even when environmental factors and spatial separation are controlled for, there is a positive correlation between advection distance and taxonomic dissimilarity, indicating that an ‘advection effect’ has a role in shaping marine microbial community composition. This effect is likely due to the advection of cells increasing the probability that upstream microorganisms will colonize downstream sites. Our study shows that in addition to distance and environmental selection, advection shapes the composition of marine microbial communities."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #53 on: September 19, 2013, 01:49:46 AM »
The linked reference shows that the new GRACE AOD1B RL05 analysis is much better (particularly for the Southern Ocean) than earlier analysis:


http://onlinelibrary.wiley.com/doi/10.1002/jgrc.20271/abstract

Dobslaw, H., F. Flechtner, I. Bergmann-Wolf, C. Dahle, R. Dill, S. Esselborn, I. Sasgen, and M. Thomas (2013), Simulating high-frequency atmosphere-ocean mass variability for dealiasing of satellite gravity observations: AOD1B RL05, J. Geophys. Res. Oceans, 118, 3704–3711, doi:10.1002/jgrc.20271.
Abstract:
"An improved version of the OMCT ocean model with 1° spatial resolution provides bottom pressure anomalies for the new release 05 of the GRACE Atmosphere and Ocean Dealiasing Level 1B (AOD1B) product. For high-frequency signals with periods below 30 days, this model explains up to 10 cm2 of the residual sea level variance seen by ENVISAT in large parts of the Southern Ocean, corresponding to about 40% of the observed sea level residuals in many open ocean regions away from the tropics. Comparable amounts of variance are also explained by AOD1B RL05 for colocated in situ ocean bottom pressure recorders. Although secular trends contained in AOD1B RL05 cause GRACE KBRR residuals to increase in shallow water regions, we find a reduction of those residuals over all open ocean areas, indicating that AOD1B RL05 is much better suited to remove nontidal high-frequency mass variability from satellite gravity observations than previous versions of AOD1B."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #54 on: November 23, 2013, 01:07:55 AM »
The following linked reference (from Nature) indicates that by 2084 projected increases in the Southern Ocean's westerly winds could contribute to a drop in local sea level of up to 40 centimeters along the Antarctic coastline, due to the Coriolis force moving the ACC away from the coast.  The reference indicates that this drop in RSLR could help stabilize the Antarctic marine glaciers; however, the reference does not discuss that such a Coriolis effect would significantly increase upwelling along the Antarctic coastline which would generally increase the amount of warm CDW in contact with the various ice shelves and grounding-lines; which would have a much larger effect on de-stabilizing the marine glaciers (than the stabilizing effect of the local sea level drop).


http://www.nature.com/news/changing-winds-dampen-antarctic-sea-level-rise-1.14189

Nature, doi:10.1038/nature.2013.14189
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #55 on: November 23, 2013, 02:07:03 AM »
I can recommend reading the article: "Tides, Critical Latitude, and their Effects on the Amundsen Sea Ice Shelves", by Robin Robertson (2013) Exchanges, No. 62 (Vol 18 No.2) August 2013, CLIVAR; which can be found in the pdf at the following link (all the other papers are good, but are not as key to ASLR):

http://www.clivar.org/sites/default/files/Exchanges/Exchanges62.pdf

This paper indicates that unless Regional Circulation Models include tidal effects their ice mass loss projections can be too low by 25 to 50%.

I can also recommend quickly reviewing the pdf found at the following link:

http://www.clivar.org/sites/default/files/SSG20/Presentations/Wednesday/22.1_OceanBasinActivities_SOP_Hellmer.pdf

Indeed, the CLIVAR website (see below) has many good pdfs of publications:

www.clivar.org
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #56 on: February 04, 2014, 01:54:33 AM »
In 1314 at the Battle of Bannockburn, the Scotts won their First War of Independence against England, and as this was my 1,314th post, I thought that I would note this historical fact.

Furthermore, I would also like to note that the prior discussion in this thread about phytoplankton in the Southern Ocean is relevant to the discussion about dust that I made in reply #60 in the Risk and Challenges for Regional Circulation Models of the Southern Ocean at the following link:

http://forum.arctic-sea-ice.net/index.php/topic,281.50.html
« Last Edit: February 04, 2014, 02:01:08 AM by AbruptSLR »
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Laurent

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Re: Trends for the Southern Ocean
« Reply #57 on: February 04, 2014, 02:25:49 PM »
Are you scottish yourself AbruptSLR !?  ;)

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #58 on: February 04, 2014, 04:20:12 PM »
Lauent,

I have a wee bit of Scottish blood in me, and note that the 700th anniversary of the victory of the Battle of Bannockburn occurs on June 24, 2014!

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #59 on: February 05, 2014, 01:28:27 AM »
I do not know much about ocean acidification, but the linked (free access) paper indicates that polar oceans are more prone to accelerated acidification than the ocean as a whole and the abstract concludes: " Our study suggests that the Amundsen Sea will become undersaturated with regard to aragonite about 40 yr sooner than predicted by models."

M. Mattsdotter Björk, A. Fransson, A. Torstensson, and M. Chierici, (2014), "Ocean acidification state in western Antarctic surface waters: controls and interannual variability", Biogeosciences, 11, 57–73, 2014, www.biogeosciences.net/11/57/2014/, doi:10.5194/bg-11-57-2014

http://www.biogeosciences.net/11/57/2014/bg-11-57-2014.pdf

This rate of acidification cannot be good for plankton and the sequestration of CO2 on the seafloor (either in the Arctic, or the Southern, Ocean).
« Last Edit: February 05, 2014, 01:36:10 AM by AbruptSLR »
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JimD

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Re: Trends for the Southern Ocean
« Reply #60 on: February 05, 2014, 04:12:25 PM »
Lauent,

I have a wee bit of Scottish blood in me, and note that the 700th anniversary of the victory of the Battle of Bannockburn occurs on June 24, 2014!

Best,
ASLR

According to our family genealogy I had ancestors (on the Scottish side) who fought in and survived that battle (course I guess if they hadn't I wouldn't be here  ;D
We do not err because truth is difficult to see. It is visible at a glance. We err because this is more comfortable. Alexander Solzhenitsyn

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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #61 on: February 05, 2014, 04:19:47 PM »
JimD,

It is nice to know that I have good company from the diaspora (I actually live in California)!

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Andreas T

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Re: Trends for the Southern Ocean
« Reply #62 on: February 08, 2014, 07:38:18 PM »
I just read this article http://www.dailykos.com/story/2013/04/10/1200602/-The-Antarctic-Half-of-the-Global-Thermohaline-Circulation-Is-Faltering# which is an interesting overview of the southern ocean. What I found particularly interesting is the link it suggests between antarctic and arctic via changing pacific / atlantic water mass exchanges.

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #63 on: February 08, 2014, 09:27:56 PM »
Andreas T,

Thanks for the link.  Some discussion of the linked topic can be found here:

http://forum.arctic-sea-ice.net/index.php/topic,214.0.html

While, I have scattered other discussion of changes in the AABW in many different threads in this folder.  This is certainly a topic of major concern and demonstrates how important the topics of the warming ocean and changes in ocean circulation patterns are on future climate change.

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #64 on: February 16, 2014, 12:08:54 PM »
The Royal Netherlands Meteorological Institute (KNMI) presents information (and the attached images) about the influence of glacial melt water on the Southern Ocean (focused on sea ice):
 
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, Volume: 6, 376–379, (2013), doi:10.1038/ngeo1767.

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."

see also: doi:10.1038/nature.2013.12709,
http://www.nature.com/news/global-warming-expands-antarctic-sea-ice-1.12709
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #65 on: February 27, 2014, 07:21:44 PM »
The linked reference states that the ACC carries 20 percent more water than previously estimated:

University of Rhode Island. "Antarctic circumpolar current carries 20 percent more water than previous estimates." ScienceDaily. ScienceDaily, 26 February 2014.

http://www.sciencedaily.com/releases/2014/02/140226165115.htm
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #66 on: March 02, 2014, 09:25:48 PM »
The following reference provides additional support for the reduction in AABW production (due to a reduction in polynas), previously cited in this folder:

Casimir de Lavergn, Jaime B. Palter, Eric D. Galbraith, Rafaele Bernardello and Irina Marinov, (2014), "Cessation of deep convection in the open Southern Ocean under anthropogenic climate change", Nature Climate Change,  DOI: 10.1038/NCLIMATE2132

http://www.sciencedaily.com/releases/2014/03/140302143515.htm


Abstract: "In 1974, newly available satellite observations unveiled the presence of a giant ice-free area, or polynya, within the Antarctic ice pack of the Weddell Sea, which persisted during the two following winters. Subsequent research showed that deep convective overturning had opened a conduit between the surface and the abyssal ocean, and had maintained the polynya through the massive release of heat from the deep sea. Although the polynya has aroused continued interest, the presence of a fresh surface layer has prevented the recurrence of deep convection there since 1976, and it is now largely viewed as a naturally rare event. Here, we present a new analysis of historical observations and model simulations that suggest deep convection in the Weddell Sea was more active in the past, and has been weakened by anthropogenic forcing. The observations show that surface freshening of the southern polar ocean since the 1950s has considerably enhanced the salinity stratification. Meanwhile, among the present generation of global climate models, deep convection is common in the Southern Ocean under pre-industrial conditions, but weakens and ceases under a climate change scenario owing to surface freshening. A decline of open-ocean convection would reduce the production rate of Antarctic Bottom Waters, with important implications for ocean heat and carbon storage, and may have played a role in recent Antarctic climate change."
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sidd

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Re: Trends for the Southern Ocean
« Reply #67 on: March 02, 2014, 09:45:59 PM »
Reduction in AABW production is happening already, see Purkey and Johnson(2013)

DOI: 10.1175/JCLI-D-12-00834.1

sidd

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #68 on: March 15, 2014, 04:27:46 PM »
The following about projected trends in ocean acidity (particularly for RCP 8.5), will greatly reduce the Southern Ocean's future ability to sequester CO2:

The three attached figures are taken from the "Ocean Acidification Summary for Policymakers – Third Symposium on the Ocean in a High-CO₂ World" (2013) (see: www.igbp.net).

The first figure shows the ocean surface pH projection through 2100 for both RCP 2.6 (blue line) and RCP 8.5 (red line).  In my opinion the blue line is for reference only.  The second attached image presents key numbers regarding ocean acidification including that the projected increase in ocean acidity by 2100 is about 170% as compared with preindustrial levels, if we continue following RCP 8.5.  The third attached image indicates that if we continue on our BAU pathway (RCP 8.5), on average 60% of the Southern Ocean surface water will be corrosive to the aragonite-shelled organisms (such as pteropods).
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #69 on: March 20, 2014, 07:32:00 PM »
The following linked reference addresses the provision of iron supplies in the Southern Ocean due to deep winter mixing:

Alessandro Tagliabue, Jean-Baptiste Sallée, Andrew R. Bowie, Marina Lévy, Sebastiaan Swart & Philip W. Boyd , (2014), "Surface-water iron supplies in the Southern Ocean sustained by deep winter mixing", Nature Geoscience, doi:10.1038/ngeo2101

http://www.nature.com/ngeo/journal/vaop/ncurrent/pdf/ngeo2101.pdf

Abstract: "Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surface waters from subsurface reservoirs, because land inputs are spatially limited. Deep mixing in winter together with year-round diffusion across density surfaces, known as diapycnal diffusion, are the main physical processes that carry iron-laden subsurface waters to the surface. Here, we analyse data on dissolved iron concentrations in the top 1,000 m of the Southern Ocean, taken from all known and available cruises to date, together with hydrographic data to determine the relative importance of deep winter mixing and diapycnal diffusion to dissolved iron fluxes at the basin scale. Using information on the vertical distribution of iron we show that deep winter mixing supplies ten times more iron to the surface ocean each year, on average, than diapycnal diffusion. Biological observations from the sub-Antarctic sector suggest that following the depletion of this wintertime iron pulse, intense iron recycling sustains productivity over the subsequent spring and summer. We conclude that winter mixing and surface-water iron recycling are important drivers of temporal variations in Southern Ocean primary production."
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Shared Humanity

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Re: Trends for the Southern Ocean
« Reply #70 on: May 09, 2014, 04:38:32 PM »
AbruptSLR.....

I've actually posted this article on a number of the Antarctic threads because, out of ignorance, I did not know where best to post. This one seems relevant.

http://www.dailykos.com/story/2014/03/05/1281907/-The-Antarctic-Half-of-the-Global-Thermohaline-Circulation-is-Collapsing

AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #71 on: May 09, 2014, 05:47:09 PM »
SH,

Thanks for providing the link, and I know how hard it is to find the right tread for some topics.

The following link leads to another thread in the Antarctic folder related to this topic; however, I think that this Trends for the Southern Ocean thread is good as well:

http://forum.arctic-sea-ice.net/index.php/topic,214.0.html

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #72 on: May 13, 2014, 12:39:13 AM »
The linked reference shows that the SAM is becoming more positive (due to AGW), which appears to be leading to a cooling of the main Antarctic continent; however, that telecommunication of energy from the Tropical Pacific is warming Western Antarctica.  Also, I note here that a positive SAM facilitates the telecommunication of Tropical Pacific energy to Western Antarctica, particularly in El Nino years:

Nerilie J. Abram, Robert Mulvaney, Françoise Vimeux Steven J. Phipps, John Turner & Matthew H. England  (2014), "Evolution of the Southern Annular Mode during the past millennium", Nature Climate Change; doi:10.1038/nclimate2235

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2235.html

Abstract: "The Southern Annular Mode (SAM) is the primary pattern of climate variability in the Southern Hemisphere, influencing latitudinal rainfall distribution and temperatures from the subtropics to Antarctica. The positive summer trend in the SAM over recent decades is widely attributed to stratospheric ozone depletion; however, the brevity of observational records from Antarctica—one of the core zones that defines SAM variability—limits our understanding of long-term SAM behaviour. Here we reconstruct annual mean changes in the SAM since AD 1000 using, for the first time, proxy records that encompass the full mid-latitude to polar domain across the Drake Passage sector. We find that the SAM has undergone a progressive shift towards its positive phase since the fifteenth century, causing cooling of the main Antarctic continent at the same time that the Antarctic Peninsula has warmed. The positive trend in the SAM since ~AD 1940 is reproduced by multimodel climate simulations forced with rising greenhouse gas levels and later ozone depletion, and the long-term average SAM index is now at its highest level for at least the past 1,000 years. Reconstructed SAM trends before the twentieth century are more prominent than those in radiative-forcing climate experiments and may be associated with a teleconnected response to tropical Pacific climate. Our findings imply that predictions of further greenhouse-driven increases in the SAM over the coming century also need to account for the possibility of opposing effects from tropical Pacific climate changes."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #73 on: June 03, 2014, 03:46:24 AM »
The linked reference provides information about a newly identified source of AABW:


Yujiro Kitade, Keishi Shimada, Takeshi Tamura, Guy D. Williams, Shigeru Aoki, Yasushi Fukamachi, Fabien Roquet, Mark Hindell, Shuki Ushio and Kay I. Ohshima, (2014), "Antarctic Bottom Water production from the Vincennes Bay Polynya, East Antarctica", Geophysical Research Letters, DOI: 10.1002/2014GL059971

http://onlinelibrary.wiley.com/doi/10.1002/2014GL059971/abstract

Abstract: "One year moorings at depths greater than 3000 m on the continental slope off Vincennes Bay, East Antarctica, reveal the cold (<−0.5°C) and fresh (<34.64) signals of newly formed Antarctic Bottom Water (AABW). The signal appeared in June, 3 months after the onset of active sea-ice production in the nearby Vincennes Bay Polynya (VBP). The AABW signal continued for about 5 months at two moorings, with 1 month delay at the western site further downstream. Ship-based hydrographic data are in agreement, detecting the westward spread of new AABW over the continental slope from VBP. On the continental shelf, Dense Shelf Water (DSW) formation is observed by instrumented seals, in and around the VBP during autumn, and we estimate its transport to be 0.16 ± 0.07 (× 106m3s−1). We conclude that the DSW formed in this region, albeit from a modest amount of sea-ice production, nonetheless contributes to the upper layer of AABW in Australian-Antarctic Basin."
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #74 on: July 12, 2014, 01:06:42 AM »
The attached figure is from the following website and it shows the approximate current location of the ARGO buoys in the Southern Ocean:

http://www.bodc.ac.uk/projects/international/argo/southern_ocean/interactive_map/
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morganism

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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #76 on: July 21, 2014, 04:07:00 AM »
morganism,

Thanks for this valuable update on the DIMES study (see Reply #8, and some earlier posts, for prior status reports on this study); you might also be interested in the discussion on risks of increasing future CO2 venting from the Southern Ocean (that is supported by the DIMES findings) in the following thread:

http://forum.arctic-sea-ice.net/index.php/topic,888.0.html

Best,
ASLR
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AbruptSLR

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Re: Trends for the Southern Ocean
« Reply #77 on: July 27, 2014, 10:29:26 PM »
The following linked reference is a compilation on multiple articles related to the Southern Ocean, carbon, and climate (change), including several that I have previously cited (in other posts in the "Southern Ocean CO2 Ventilation" thread in the "Science" folder and elsewhere in the "Antarctic" folder) and two of which are cited after the link:

Andrew J. Watson, Michael P. Meredith, and John Marshall, (2014), "Introduction: The Southern Ocean, carbon and climate", Phil. Trans. R. Soc. A., 372 2019 20130057; doi:10.1098/rsta.2013.0057

http://rsta.royalsocietypublishing.org/content/372/2019.toc



Steven M. A. C. van Heuven, Mario Hoppema, Elizabeth M. Jones and Hein J. W. de Baar, (2014), "Rapid invasion of anthropogenic CO2 into the deep circulation of the Weddell Gyre", Phil. Trans. R. Soc. A., 372 20130056; doi:10.1098/rsta.2013.0056

Abstract: "Data are presented for total carbon dioxide (TCO2), oxygen and nutrients from 14 cruises covering two repeat sections across the Weddell Gyre, from 1973 to 2010. Assessments of the rate of increase in anthropogenic CO2 (Cant) are made at three locations. Along the Prime Meridian, TCO2 is observed to steadily increase in the bottom water. Accompanying changes in silicate, nitrate and oxygen confirm the non-steady state of the Weddell circulation. The rate of increase in TCO2 of +0.12±0.05 μmol kg−1 yr−1 therefore poses an upper limit to the rate of increase in Cant. By contrast, the bottom water located in the central Weddell Sea exhibits no significant increase in TCO2, suggesting that this water is less well ventilated at the southern margins of the Weddell Sea. At the tip of the Antarctic Peninsula (i.e. the formation region of the bottom water found at the Prime Meridian), the high rate of increase in TCO2 over time observed at the lowest temperatures suggests that nearly full equilibration occurs with the anthropogenic CO2 of the atmosphere. This observation constitutes rare evidence for the possibility that ice cover is not a major impediment for uptake of Cant in this prominent deep water formation region."


Joseph D. Majkut, Brendan R. Carter, Thomas L. Frölicher, Carolina O. Dufour, Keith B. Rodgers and Jorge L. Sarmiento, (2014), "An observing system simulation for Southern Ocean carbon dioxide uptake", Phil. Trans. R. Soc. A., 372 20130046; doi:10.1098/rsta.2013.0046

Abstract: "The Southern Ocean is critically important to the oceanic uptake of anthropogenic CO2. Up to half of the excess CO2 currently in the ocean entered through the Southern Ocean. That uptake helps to maintain the global carbon balance and buffers transient climate change from fossil fuel emissions. However, the future evolution of the uptake is uncertain, because our understanding of the dynamics that govern the Southern Ocean CO2 uptake is incomplete. Sparse observations and incomplete model formulations limit our ability to constrain the monthly and annual uptake, interannual variability and long-term trends. Float-based sampling of ocean biogeochemistry provides an opportunity for transforming our understanding of the Southern Ocean CO2 flux. In this work, we review current estimates of the CO2 uptake in the Southern Ocean and projections of its response to climate change. We then show, via an observational system simulation experiment, that float-based sampling provides a significant opportunity for measuring the mean fluxes and monitoring the mean uptake over decadal scales."
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Re: Trends for the Southern Ocean
« Reply #78 on: August 15, 2014, 12:47:29 AM »
The linked reference indicates that observed and projected reductions in deep convection in the Southern Ocean due to climate change, will result in a continuing reduction in AABW production which represents a positive feedback for global warming.


Casimir de Lavergne, Jaime B. Palter, Eric D. Galbraith, Raffaele Bernardello & Irina Marinov, (2014), "Cessation of deep convection in the open Southern Ocean under anthropogenic climate change", Nature Climate Change, 4, 278–282, doi:10.1038/nclimate2132


http://www.nature.com/nclimate/journal/v4/n4/full/nclimate2132.html


Abstract: "In 1974, newly available satellite observations unveiled the presence of a giant ice-free area, or polynya, within the Antarctic ice pack of the Weddell Sea, which persisted during the two following winters. Subsequent research showed that deep convective overturning had opened a conduit between the surface and the abyssal ocean, and had maintained the polynya through the massive release of heat from the deep sea. Although the polynya has aroused continued interest, the presence of a fresh surface layer has prevented the recurrence of deep convection there since 1976, and it is now largely viewed as a naturally rare event. Here, we present a new analysis of historical observations and model simulations that suggest deep convection in the Weddell Sea was more active in the past, and has been weakened by anthropogenic forcing. The observations show that surface freshening of the southern polar ocean since the 1950s has considerably enhanced the salinity stratification. Meanwhile, among the present generation of global climate models, deep convection is common in the Southern Ocean under pre-industrial conditions, but weakens and ceases under a climate change scenario owing to surface freshening. A decline of open-ocean convection would reduce the production rate of Antarctic Bottom Waters, with important implications for ocean heat and carbon storage, and may have played a role in recent Antarctic climate change."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #79 on: October 01, 2014, 05:09:34 PM »
The following link leads to an Internet website (for sciencecodex) that discusses (see extract below) recent research published in Nature Communications showing that current Southern Ocean waters are becoming more layered with cold water on top and warm water below; which promotes ice melting near the grounding lines of Antarctic marine glaciers, as occurred 14,000 years ago during the Meltwater Pulse 1A.  This clear indicates an increasing risk of multiple meters of SLR this century:

http://www.sciencecodex.com/changing_antarctic_waters_could_trigger_steep_rise_in_sea_levels-142713

Extract: "The research published in Nature Communications found that in the past, when ocean temperatures around Antarctica became more layered - with a warm layer of water below a cold surface layer - ice sheets and glaciers melted much faster than when the cool and warm layers mixed more easily.

This defined layering of temperatures is exactly what is happening now around the Antarctic.
"The reason for the layering is that global warming in parts of Antarctica is causing land-based ice to melt, adding massive amounts of freshwater to the ocean surface," said ARC Centre of Excellence for Climate System Science researcher Prof Matthew England an author of the paper.
"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers on Pine Island and Totten. It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.""
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Re: Trends for the Southern Ocean
« Reply #80 on: October 06, 2014, 02:49:32 AM »
This reference is so important (with regard to ocean heat content, SLR, planetary energy budget and climate sensitivity) that I am posting it both here and in the "Forcing" thread:

Paul J. Durack, Peter J. Gleckler, Felix W. Landerer and Karl E. Taylor, (2014), "Quantifying Underestimates of Long-term Upper-Ocean Warming", Nature Climate Change, 4 (11), DOI: 10.1038/nclimate2389

http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/140926a_Duracketal_UpperOceanWarming.pdf

Abstract: "The global ocean stores more than 90% of the heat associated with observed greenhouse‐gas‐attributed global warming (Levitus et al., 2005; Church et al., 2011; Otto et al., 2013; Rhein et al., 2013). Using satellite altimetry observations and a large suite of climate models, we conclude that observed estimates of 0‐700 dbar global ocean warming since 1970 are likely biased low. This underestimation is attributed to poor sampling of the Southern Hemisphere, and limitations of the analysis methods that conservatively estimate temperature changes in data‐sparse regions (Gregory et al., 2004; Gouretski & Koltermann, 2007; Gille, 2008). We find that the partitioning of northern and southern hemispheric simulated sea surface height changes are consistent with precise altimeter observations, whereas the hemispheric partitioning of simulated upper‐ocean warming is inconsistent with observed in‐situ‐based ocean heat content estimates. Relying on the close correspondence between hemispheric‐scale ocean heat content and steric changes, we adjust the poorly constrained Southern Hemisphere observed warming estimates so that hemispheric ratios are consistent with the broad range of modelled results. These adjustments yield large increases (2.2‐7.1 x 1022 J 35yrs‐1) to current global upper‐ocean heat content change estimates, and have important implications for sea level, the planetary energy budget and climate sensitivity assessments."

See also:
http://www-pcmdi.llnl.gov/about/staff/Durack/dump/oceanwarming/

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #81 on: October 06, 2014, 06:23:56 AM »
Do you recall Durack(2012) DOI: 10.1126/science.1212222  where they inferred from salinity changes that the water cycle had intensified at twice the rate predicted by models ? That was a nice paper, he does good work.

In the context of his latest, i will point out Llovel(2014) DOI: 10.1038/NCLIMATE2387 which detects no heat going below 2000m, albeit with large uncertainty. I am still chewing on this, but i thought i would point it out.

sidd

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Re: Trends for the Southern Ocean
« Reply #82 on: October 06, 2014, 07:24:45 PM »
sidd,

I agree that Durack appears to be one of the good ones (making a real difference), and all of his publications are worth looking at (see link below to a website with his publication):

http://www-pcmdi.llnl.gov/about/staff/Durack/publication/

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #83 on: October 06, 2014, 11:56:05 PM »
sidd,

As the topics raised by the Durack et al (2014) paper are more wide spread than just those related to the Southern Ocean, I have posted some information in the following thread, in the Science folder:

http://forum.arctic-sea-ice.net/index.php/topic,1011.0.html

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

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Re: Trends for the Southern Ocean
« Reply #84 on: October 15, 2014, 12:01:48 AM »
For those who want to have an accurate baseline for hydrography and circulation in the Filchner Depression, Weddell Sea, for reference and this pattern changes due to climate change, then the following is a very good reference:

Darelius, E., K. Makinson, K. Daae, I. Fer, P. R. Holland, and K. W. Nicholls (2014), Hydrography and circulation in the Filchner Depression, Weddell Sea, Antarctica, J. Geophys. Res. Oceans, 119, doi:10.1002/2014JC010225.

http://onlinelibrary.wiley.com/doi/10.1002/2014JC010225/abstract

Abstract: "Cold and dense ice shelf water (ISW) emerging from the Filchner-Ronne Ice Shelf cavity in the southwestern Weddell Sea flows northward through the Filchner Depression to eventually descend the continental slope and contribute to the formation of bottom water. New ship-born observations of hydrography and currents from Filchner Depression in January 2013 suggest that the northward flow of ISW takes place in a middepth jet along the eastern flank of the depression, thus questioning the traditional view with outflow along the western flank. This interpretation of the data is supported by results from a regional numerical model, which shows that ISW flowing northward along the eastern coast of Berkner Island turns eastward and crosses the depression to its eastern side upon reaching the Filchner ice front. The ice front represents a sudden change in the thickness of the water column and thus a potential vorticity barrier. Transport estimates of northward ISW flux based on observations ranges from 0.2 to 1.0 Sv."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #85 on: October 31, 2014, 11:21:33 PM »
The linked provides high-resolution model projections that the continuing poleward shifted circumpolar winds will rapidly increase subsurface water temperatures of the ocean water beneath Antarctic ice shelves and grounding lines for marine glaciers (which is bad news wrt sea level rise):

Spence, P., S. M. Griffies, M. H. England, A. M. C. Hogg, O. A. Saenko, and N. C. Jourdain (2014), Rapid subsurface warming and circulation changes of Antarctic coastal waters by poleward shifting winds, Geophys. Res. Lett., 41, 4601–4610, doi:10.1002/2014GL060613

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060613/abstract

Abstract: "The southern hemisphere westerly winds have been strengthening and shifting poleward since the 1950s. This wind trend is projected to persist under continued anthropogenic forcing, but the impact of the changing winds on Antarctic coastal heat distribution remains poorly understood. Here we show that a poleward wind shift at the latitudes of the Antarctic Peninsula can produce an intense warming of subsurface coastal waters that exceeds 2°C at 200–700 m depth. The model simulated warming results from a rapid advective heat flux induced by weakened near-shore Ekman pumping and is associated with weakened coastal currents. This analysis shows that anthropogenically induced wind changes can dramatically increase the temperature of ocean water at ice sheet grounding lines and at the base of floating ice shelves around Antarctica, with potentially significant ramifications for global sea level rise."

See also the extracts from the following summary SciAm article:

http://www.scientificamerican.com/article/an-ill-wind-blows-in-antarctica-threatens-global-flooding/


Extract: "The effects of wind changes, which were found to potentially increase temperatures in the Southern Ocean between 660 feet and 2,300 feet below the surface by 2°C, or nearly 3.6°F, are over and above the ocean warming that’s being caused by the heat-trapping effects of greenhouse gases. “We’re not even adding heat to the ocean,” Griffies said of the modeling effort.
The discovery accompanies more bad news for the future of Antarctica’s ice, which was published a month ago in Nature Communications. A cold layer of freshwater that’s sitting at the ocean surface around Antarctica, caused by melting ice and contributing to the expansion of sea ice, was found through climate modeling to be preventing warm water from reaching the surface, where it would normally cool. Instead, that warm water, which is shuttled south by underwater currents from the tropics, is being thrust against Antarctica’s ice sheet and its ice shelves, exacerbating melting and hastening sea level rise.

“The pattern and magnitude of warming shown in this [Geophysical Research Letters] study is alarming,” said Nick Golledge, a Victoria University of Wellington researcher who led the Nature Communications study. “Since they use a very high-resolution model, they are able to capture behavior that most models cannot simulate, so it's a great piece of work.”"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #86 on: November 10, 2014, 05:21:45 PM »
The linked research indicates that ocean surface warming across multiple oceans has contributed to the recent faux atmospheric surface temperature "hiatus", and that multiple mechanisms are at play including the recent trend toward positive SAM values in the Southern Ocean:

S. S. Drijfhout, A. T. Blaker, S. A. Josey, A. J. G. Nurser, B. Sinha and M. A. Balmaseda, (2014), "Surface warming hiatus caused by increased heat uptake across multiple ocean basins" Geophysical Research Letters, DOI: 10.1002/2014GL061456

http://onlinelibrary.wiley.com/doi/10.1002/2014GL061456/abstract

Abstract: "The first decade of the twenty-first century was characterised by a hiatus in global surface warming. Using ocean model hindcasts and reanalyses we show that heat uptake between the 1990s and 2000s increased by 0.7 ± 0.3Wm−2. Approximately 30% of the increase is associated with colder sea surface temperatures in the eastern Pacific. Other basins contribute via reduced heat loss to the atmosphere, in particular the Southern and subtropical Indian Oceans (30%), and the subpolar North Atlantic (40%). A different mechanism is important at longer timescales (1960s-present) over which the Southern Annular Mode trended upwards. In this period, increased ocean heat uptake has largely arisen from reduced heat loss associated with reduced winds over the Agulhas Return Current and southward displacement of Southern Ocean westerlies."

See also:

http://www.reportingclimatescience.com/news-stories/article/heat-uptake-by-several-oceans-drives-pause-says-study.html
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #87 on: November 10, 2014, 08:17:18 PM »
That is a nice paper by Drifthous et al., I notice that Balmaseda is an author. The first thing that jumps out at me are Figs S6 b) and c), which show clearly the freshening and surface cooling of the Southern ocean and the warming below. I shall have to stare at those figures and the whole  paper for a while.

sidd

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Re: Trends for the Southern Ocean
« Reply #88 on: November 10, 2014, 10:13:39 PM »
That is a nice paper by Drifthous et al., I notice that Balmaseda is an author. The first thing that jumps out at me are Figs S6 b) and c), which show clearly the freshening and surface cooling of the Southern ocean and the warming below. I shall have to stare at those figures and the whole  paper for a while.

sidd

sidd,

Many people focus primarily on GHG when they consider climate change, but the ozone hole over Antarctica has accelerated the westeries in the Southern Ocean for decades now; which has caused the positive trend in the SAM; which has caused the ice shelf/sheet melting; which has spread cold fresh water around the surface of the Southern Ocean; which has protected the deeper water from the cold atmosphere; which contributes to both greater ocean heat content and more ice shelf/sheet melting.  This vicious cycle will result in sea level rise rates that exceed the RCP projections because the current AOGCM projections do not correctly model such feedback mechanisms; even though James Hansen has been discussing this mechanism for a long time now.  By the time (7-years from now) that the ACME's Earth System Model (by the DoE) has correctly modeled such feedback mechanisms, I suspect that the accelerating collapse of the Amundsen Sea Sector marine glaciers will be obvious to all, even without the sophisticated ESM projections.

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #89 on: December 08, 2014, 04:08:09 PM »
The following quote comes from the linked discussion about new research from the linked reference from Schmidtko et al 2014 about a new analysis of decade old trends of seawater properties adjacent to Antarctica.  This research not only adds definition to the problem of advected-CDW driven grounding line retreat of marine glaciers in the Bellingshausen and Amundsen Sea areas but also warns about a trend of warm CDW encroachment beneath the FRIS:

http://arstechnica.com/science/2014/12/why-are-some-antarctic-ice-shelves-feeling-warmer-water-than-others/

Quote: "Between the temperature and salinity patterns, they could evaluate different causes of the observed warming. The Circumpolar Deep Water jumps out, as it has been both warming and moving upward to influence shallower water in many places. (At rates of up to 50 meters per decade in the Bellingshausen and Amundsen Seas, for example.) That seems to be the biggest change for the water beneath the ice shelves.
The movement of the Circumpolar Deep Water isn’t occurring everywhere, and that’s because of wind patterns. In most places, the wind pushes surface water landward, thickening the surface layer over the continental shelf. That actually forms a lid that keeps the Circumpolar Deep Water from leaking up over the continental slope and onto the shelf. But in some places, the wind does the opposite, pulling the Circumpolar Deep Water up onto the shelf. Greenhouse warming and the loss of ozone both act to intensify the winds responsible for these two configurations, and that seems to account for the strong warming of some shelf waters. Add in the fact that the Circumpolar Deep Water is warmer than it used to be, and you’ve got a recipe for melting ice shelves.
This activity in the Amundsen Sea is contributing to the likely irreversible, long-term loss of ice from parts of the West Antarctic Ice Sheet. And that’s not the only part of the ice sheet that could face a similar invasion of warmth from the sea. There’s a potential exception to the rule of landward-blowing winds providing protection in the southern part of the Weddell Sea, where that surface water lid has been lifting and allowing Circumpolar Deep Water to climb the continental slope, the researchers note, “which raises questions about the future stability of [continental shelf bottom water] temperatures in front of the Filchner and Ronne ice shelves.”"


Sunke Schmidtko, Karen J. Heywood, Andrew F. Thompson & Shigeru Aoki, (2014), "Multidecadal warming of Antarctic waters", Science 5 December, Vol. 346 no. 6214 pp. 1227-1231, DOI: 10.1126/science.1256117

http://www.sciencemag.org/content/346/6214/1227

Abstract: "Decadal trends in the properties of seawater adjacent to Antarctica are poorly known, and the mechanisms responsible for such changes are uncertain. Antarctic ice sheet mass loss is largely driven by ice shelf basal melt, which is influenced by ocean-ice interactions and has been correlated with Antarctic Continental Shelf Bottom Water (ASBW) temperature. We document the spatial distribution of long-term large-scale trends in temperature, salinity, and core depth over the Antarctic continental shelf and slope. Warming at the seabed in the Bellingshausen and Amundsen seas is linked to increased heat content and to a shoaling of the mid-depth temperature maximum over the continental slope, allowing warmer, saltier water greater access to the shelf in recent years. Regions of ASBW warming are those exhibiting increased ice shelf melt."

See also:

http://www.sciencemag.org/content/346/6214/1180

Extract: "Nobody lives permanently in Antarctica. At first glance, studies of Antarctic climate might thus seem like a curiosity without obvious societal implications. Yet, if the entire West Antarctic Ice Sheet were to melt, global sea level would rise by 4.8 m, with major effects on coastal populations. Two studies published earlier this year offered convincing evidence that the West Antarctic Ice Sheet is indeed melting irrevocably (1, 2). What are the processes behind this melting? On page 1227 of this issue, Schmidtko et al. (3) show that the water flowing under the ice shelves has warmed in recent decades and that upwelling winds at the continental shelf break may contribute to this process."
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Re: Trends for the Southern Ocean
« Reply #90 on: December 15, 2014, 11:18:14 PM »
For those that are less literate in science jargon, a good summary can be found http://www.climatecentral.org/news/warm-water-invasion-fueling-striking-antarctic-ice-melt-18401 .
As opposed this http://www.nasa.gov/press/2014/october/nasa-study-finds-earth-s-ocean-abyss-has-not-warmed/ , it is obvious that oceans are continuing to warm and maybe just now we are getting an idea of how much and how the oceans are reacting to it.
"All truth passes through three stages: First, it is ridiculed; Second,  it is violently opposed; and Third, it is accepted as self-evident."
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Re: Trends for the Southern Ocean
« Reply #91 on: March 03, 2015, 06:45:39 PM »
The linked article points to a PNAS 2015 article indicating that icebergs are breaking away from the Antarctic coastline & smaller ice-shelves, faster than previously thought.  This appears to be related to the higher than expected impact of warm ocean water on Antarctic glacial ice.

http://www.businessinsider.com.au/icebergs-are-breaking-away-from-antarctica-faster-than-previously-thought-2015-3
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Re: Trends for the Southern Ocean
« Reply #92 on: March 12, 2015, 02:52:55 PM »
The linked reference indicates that for the past several decades (i.e. since the Antarctic ozone hole formed) the increasing wind velocities over the Southern Ocean have increasingly created small oceanic eddy fields that has helped to sequester both surface heat and CO₂ into the Southern Ocean.  What the authors do not emphasize includes: (a) as the Antarctic ozone hole heals itself (which has already begun) the westerly wind velocities will either stabilize, or possibly slow, which will either cap, or reverse this heat/CO₂ absorption; (b) these eddies can increase upwelling that can also increase venting of organic carbon from the Southern Ocean (which partially offsets the absorption); and (c) the rapid acidification of the water in the Southern Ocean will soon start to reduce the amount of CO₂ sequestered by some of the plankton down under.

Hogg, A. McC., M. P. Meredith, D. P. Chambers, E. P. Abrahamsen, C. W. Hughes, and A. K. Morrison (2015), "Recent trends in the Southern Ocean eddy field", J. Geophys. Res. Oceans, 120, 257–267, doi:10.1002/2014JC010470.


http://onlinelibrary.wiley.com/doi/10.1002/2014JC010470/abstract



Abstract: "Eddies in the Southern Ocean act to moderate the response of the Antarctic Circumpolar Current (ACC) to changes in forcing. An updated analysis of the Southern Ocean satellite altimetry record indicates an increase in eddy kinetic energy (EKE) in recent decades, contemporaneous with a probable decrease in ACC transport. The EKE trend is largest in the Pacific (14.9 ± 4.1 cm2 s−2 per decade) and Indian (18.3 ± 5.1 cm2 s−2 per decade) sectors of the Southern Ocean. We test the hypothesis that variations in wind stress can account for the observed EKE trends using perturbation experiments conducted with idealized high-resolution ocean models. The decadal increase in EKE is most likely due to continuing increases in the wind stress over the Southern Ocean, albeit with considerable interannual variability superposed. ACC transport correlates well with wind stress on these interannual time scales, but is weakly affected by wind forcing at longer periods. The increasing intensity of the Southern Ocean eddy field has implications for overturning circulation, carbon cycling, and climate."


See also:

http://www.reportingclimatescience.com/news-stories/article/wind-driven-eddies-push-ocean-heat-deep-says-study.html

Extract: "The increasing strength of winds over the Southern Ocean has extended its ability to absorb carbon dioxide, effectively delaying the impacts of global warming.
New research published in the Journal of Geophysical Research and using National Computational Infrastructure found the intensifying wind over that ocean increased the speed and energy of eddies and jets, which are responsible in large part for the movement of nutrients, heat and salt across the ocean basin.
The increased movement and overturning of these eddies and jets has accelerated the carbon cycle and driven more heat into the deep ocean."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #93 on: September 10, 2015, 10:22:48 PM »
The linked reference's conclusion that the Southern Ocean's dynamic ocean carbon cycle varies more in time than previously recognized, is not very reassuring to me:


Peter Landschützer, Nicolas Gruber, F. Alexander Haumann, Christian Rödenbeck, Dorothee C. E. Bakker, Steven van Heuven, Mario Hoppema, Nicolas Metzl, Colm Sweeney, Taro Takahashi, Bronte Tilbrook and Rik Wanninkhof (11 September 2015), "The reinvigoration of the Southern Ocean carbon sink", Science, Vol. 349 no. 6253 pp. 1221-1224, DOI: 10.1126/science.aab2620

http://www.sciencemag.org/content/349/6253/1221.abstract


Abstract: "Several studies have suggested that the carbon sink in the Southern Ocean—the ocean’s strongest region for the uptake of anthropogenic CO2 —has weakened in recent decades. We demonstrated, on the basis of multidecadal analyses of surface ocean CO2 observations, that this weakening trend stopped around 2002, and by 2012, the Southern Ocean had regained its expected strength based on the growth of atmospheric CO2. All three Southern Ocean sectors have contributed to this reinvigoration of the carbon sink, yet differences in the processes between sectors exist, related to a tendency toward a zonally more asymmetric atmospheric circulation. The large decadal variations in the Southern Ocean carbon sink suggest a rather dynamic ocean carbon cycle that varies more in time than previously recognized."

S. E. Mikaloff-Fletcher (11 September 2015), "An increasing carbon sink?", Science, Vol. 349 no. 6253 p. 1165, DOI: 10.1126/science.aad0912


http://www.sciencemag.org/content/349/6253/1165.short
 

Abstract: Since 1870, Earth's oceans have absorbed more than one-quarter of the carbon dioxide emitted to the atmosphere from fossil fuel burning and other human activities, thereby dramatically slowing climate change. The Southern Ocean is responsible for ~40% of this global ocean carbon sink. Recent studies have suggested that the rate of carbon uptake by the Southern Ocean may be slowing. Such a positive climate feedback effect would reduce the Southern Ocean's capacity to slow climate change. On page 1221 of this issue, Landschützer et al. show that although the rate of carbon uptake by the Southern Ocean slowed between the 1980s and early 2000s, it began to strengthen again in 2002 and continued to do so until at least 2012."


See also:
http://www.theguardian.com/environment/2015/sep/10/southern-ocean-showing-remarkable-revival-in-carbon-absorption-ability

http://www.news24.com/Green/News/Southern-Ocean-soaks-up-more-greenhouse-gases-20150910
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Re: Trends for the Southern Ocean
« Reply #94 on: September 12, 2015, 05:07:38 PM »
The linked research presents a 13-year (2002-2015) time-series of CO₂ partial pressure readings of surface waters in Drakes Passage (see the first attached image) taken by the Antarctic Research Supply Vessel Laurence M. Gould; which indicates that a relatively recent increase in winter overturning of deep water is contributing to the relatively recent strengthening of CO₂ absorption by the Southern Ocean (see the second image):

David R. Munro, Nicole S. Lovenduski, Taro Takahashi, Britton B. Stephens, Timothy Newberger and Colm Sweeney (2015), "Recent evidence for a strengthening CO2sink in the Southern Ocean from carbonate system measurements in the Drake Passage (2002-2015)", Geophysical Research Letters, DOI: 10.1002/2015GL065194


http://onlinelibrary.wiley.com/doi/10.1002/2015GL065194/abstract


Abstract: "We present a 13-year (2002–2015) semi-monthly time-series of the partial pressure of CO2 in surface water (pCO2surf) and other carbonate system parameters from the Drake Passage. This record shows a clear increase in the magnitude of the sea-air pCO2 gradient, indicating strengthening of the CO2 sink in agreement with recent large-scale analyses of the world oceans. The rate of increase in pCO2surf north of the Antarctic Polar Front (APF) is similar to the atmospheric pCO2 (pCO2atm) trend, whereas the pCO2surf increase south of the APF is slower than the pCO2atm trend. The high-frequency surface observations indicate that an absence of a winter increase in total CO2 (TCO2) and cooling summer sea surface temperatures are largely responsible for increasing CO2 uptake south of the APF. Muted winter trends in surface TCO2 also provide temporary stability to the carbonate system that is already close to undersaturation with respect to aragonite."


Caption for the second image: "This figure shows the time series trend in ΔpCO2 (gray) for Region 4 south of the Antarctic Polar Front, with winter observations and trend in blue. The ΔpCO2 is the difference between the partial pressures of CO2 in the ocean and the overlying atmosphere. A decline in ΔpCO2 corresponds to an increase in ocean CO2 uptake."

See also:
http://www.reportingclimatescience.com/news-stories/article/two-papers-highlight-southern-ocean-co2-sink.html

Extract: "By analyzing more than one million surface ocean observations, the researchers could tease out subtle differences between the carbon dioxide trends in the surface ocean and the atmosphere that suggest a strengthening of the carbon sink. This change is most pronounced in the southern half of the Drake Passage during winter (see Figure 2). Although the researchers aren’t sure of the exact mechanism driving these changes, “it’s likely that winter mixing with deep waters that have not had contact with the atmosphere for several hundred years plays an important role,” says Munro."
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Re: Trends for the Southern Ocean
« Reply #95 on: September 20, 2015, 01:28:04 AM »
The linked reference (with an open access pdf) presents paleo-evidence from the past 30,000 years to show that seasonal mixing of the upper portions of the Southern Ocean during low sea ice periods; complicates the interpretation of the associated carbon-cycle in the Southern Ocean with regards to sea ice extent.  Hopefully, this new research will be incorporated into advanced ESM's such as ACME.

Andrea Abelmann, Rainer Gersonde, Gregor Knorr, Xu Zhang, Bernhard Chapligin, Edith Maier, Oliver Esper, Hans Friedrichsen, Gerrit Lohmann, Hanno Meyer und Ralf Tiedemann (2015), "The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink", Nature Communications, doi: 10.1038/ncomms9136.

http://www.nature.com/ncomms/2015/150918/ncomms9136/abs/ncomms9136.html
http://www.nature.com/ncomms/2015/150918/ncomms9136/pdf/ncomms9136.pdf

Abstract: "Reduced surface–deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface–subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring–summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall–winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #96 on: November 03, 2015, 04:37:04 PM »
In the category of very unhappy news, the linked Nature Climate Change reference indicates an abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean beginning circa 2040.  While some people are happy about the continued relatively high rate of CO₂ uptake by the Southern Ocean, the consequence of the associated ocean acidification will be unpleasant (see attached image):

Claudine Hauri, Tobias Friedrich & Axel Timmermann (2015), "Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean", Nature Climate Change, doi:10.1038/nclimate2844


http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2844.html

http://www.nature.com/articles/nclimate2844.epdf?referrer_access_token=loGp3jlDd1gWk4fK37tbDNRgN0jAjWel9jnR3ZoTv0MfSWwthBCfdFt7gar9GUUIaafDmr0WnhODt8AbZ4KTSgZcQoYMrEpq6B7RfrXkXxlVXhOIkdJkpC9sbxfai3T9KBEoCop7vnXIZaMb8pMBMQztCQb36nMX3ru1Vfsfbd5HMmUV8L2LQ-qXjTiklB4cORejlMczATyjuLs9iNFSF0XmeqLGtqhsJga4lvvGStKRC7ENdIIKfAMzbOXdOQ6r4Cp1IvVOmnIkjLYkaA4l8aRhEeJE6hm8rC1lLVaJPQcF3Ijqirv8CndKJStVAo7K&tracking_referrer=www.smh.com.au

Abstract: "Ocean acidification may lead to seasonal aragonite undersaturation in surface waters of the Southern Ocean as early as 2030. These conditions are harmful to key organisms such as pteropods, which contribute significantly to the pelagic foodweb and carbon export fluxes in this region. Although the severity of ocean acidification impacts is mainly determined by the duration, intensity and spatial extent of aragonite undersaturation events, little is known about the nature of these events, their evolving attributes and the timing of their onset in the Southern Ocean. Using an ensemble of ten Earth system models, we show that starting around 2030, aragonite undersaturation events will spread rapidly, affecting ~30% of Southern Ocean surface waters by 2060 and >70% by 2100, including the Patagonian Shelf. On their onset, the duration of these events will increase abruptly from 1 month to 6 months per year in less than 20 years in >75% of the area affected by end-of-century aragonite undersaturation. This is likely to decrease the ability of organisms to adapt to a quickly evolving environment. The rapid equatorward progression of surface aragonite undersaturation can be explained by the uptake of anthropogenic CO2, whereas climate-driven physical or biological changes will play a minor role."

http://www.smh.com.au/environment/climate-change/abrupt-changes-in-food-chains-predicted-as-southern-ocean-acidifies-fast-study-20151030-gknd2g.html
Extract: " The Southern Ocean is acidifying at such a rate because of rising carbon dioxide emissions that large regions may be inhospitable for key organisms in the food chain to survive as soon as 2030 …"
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #97 on: January 30, 2016, 12:46:40 AM »
The linked article discusses NCAR's airborne field campaign to monitor oxygen and CO₂ exchange between the atmosphere & the Southern Ocean:

http://phys.org/news/2016-01-nasa-airborne-antarctic-seas.html

Extract: "Called ORCAS, the field campaign will provide a rare look at how oxygen and carbon dioxide are exchanged between the air and the Southern Ocean. The campaign is led by the National Center for Atmospheric Research (NCAR). Michelle Gierach of NASA's Jet Propulsion Laboratory, Pasadena, California, is a principal investigator, along with other scientists from a range of universities and research institutions.
Carbon dioxide is the main greenhouse gas contributing to human-caused climate change. As more carbon dioxide has been released into the atmosphere by the burning of fossil fuels, the ocean has stepped up the amount of the gas it absorbs from the air. But it's unclear whether the ocean can keep pace with continued emissions.
Previous studies have disagreed about whether the Southern Ocean's ability to absorb carbon dioxide is speeding up or slowing down. The measurements and air samples collected by ORCAS—which stands for the O2/N2 Ratio and CO2 Airborne Southern Ocean Study—will give scientists critical data to help clarify what's happening in the remote region.
The researchers plan to make 14 flights out of Punta Arenas, Chile, across parts of the Southern Ocean during the campaign, which ends Feb. 28. A suite of instruments will measure the distribution of oxygen and carbon dioxide, as well as other gases produced by marine microorganisms, microscopic airborne particles and clouds. The flights also will observe ocean color—which can indicate how much and what type of phytoplankton is in the water—using NASA's Portable Remote Imaging Spectrometer (PRISM). The scientists hope that adding these other measurements to the carbon dioxide data will give them new insight on chemical, physical and biological processes that are affecting the ocean's ability to absorb the greenhouse gas."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #98 on: April 08, 2016, 04:54:24 PM »
The linked reference discusses the use of GRACE as a new tool for monitoring changes in the AABW.  The initial study found that the AABW transport into the Pacific Ocean from 2003 to 2014 was highly variable and that no clear trend signal was identified:

Matthew R. Mazloff & Carmen Boening (5 April 2016), "Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE", Geophysical Research Letter, DOI: 10.1002/2016GL068474


http://onlinelibrary.wiley.com/doi/10.1002/2016GL068474/abstract

Abstract: "Air-ice-ocean interactions in the Antarctic lead to formation of the densest waters on Earth. These waters convect and spread to fill the global abyssal oceans. The heat and carbon storage capacity of these water masses, combined with their abyssal residence times that often exceeds centuries, makes this circulation pathway the most efficient sequestering mechanism on Earth. Yet monitoring this pathway has proven challenging due to the nature of the formation processes and the depth of the circulation. The Gravity Recovery and Climate Experiment (GRACE) gravity mission is providing a time-series of ocean mass redistribution, and offers a transformative view of the abyssal circulation. Here we use the GRACE measurements to infer, for the first time, a 2003–2014 time-series of Antarctic Bottom Water export into the South Pacific. We find this export highly variable, with a standard deviation of 1.87 Sv and a decorrelation timescale of less than one month. A significant trend is undetectable."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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Re: Trends for the Southern Ocean
« Reply #99 on: July 15, 2016, 05:29:08 PM »
The linked reference measures gas contents in Southern Ocean water to monitor (among other things) the formation of Antarctic Bottom Water, AABW. While it is intriguing that such research offers the prospect of measuring gases though-out the AABW extent to fingerprint paleo conditions in the Southern Ocean; I also note that the observed entrainment of significant quantities of glacial meltwater in the AABW also results in a slowing of the thermohaline ocean circulation; which serves to verify the ice-climate interaction feedback cited by Hansen:

Brice Loose, William J. Jenkins, Roisin Moriarty, Peter Brown, Loic Jullion, Alberto C. Naveira Garabato, Sinhue Torres Valdes, Mario Hoppema, Chris Ballentine & Michael P. Meredith (16 June 2016), "Estimating the recharge properties of the deep ocean using noble gases and helium isotopes", Journal of Geophysical Research: Oceans, DOI: 10.1002/2016JC011809

http://onlinelibrary.wiley.com/doi/10.1002/2016JC011809/full

Abstract: "The distribution of noble gases and helium isotopes in the dense shelf waters of Antarctica reflect the boundary conditions near the ocean surface: air-sea exchange, sea ice formation and subsurface ice melt. We use a non-linear least-squares solution to determine the value of the recharge temperature and salinity, as well as the excess air injection and glacial meltwater content throughout the water column and in the precursor to Antarctic Bottom Water. The noble gas-derived recharge temperature and salinity in the Weddell Gyre are -1.95 °C and 34.95 psu near 5500 m; these cold, salty recharge values are a result of surface cooling as well as brine rejection during sea ice formation in Antarctic polynyas. In comparison, the global value for deep water recharge temperature is -0.44 °C at 5500 m, which is 1.5 °C warmer than the southern hemisphere deep water recharge temperature, reflecting the contribution from the north Atlantic. The contrast between northern and southern hemisphere recharge properties highlight the impact of sea ice formation on setting the gas properties in southern sourced deep water. Below 1000 m, glacial meltwater averages 3.5 ‰ by volume and represents greater than 50% of the excess neon and argon found in the water column. These results indicate glacial melt has a non-negligible impact on the atmospheric gas content of Antarctic Bottom Water."

See also:

Yan, W. (2016), How do the deep waters of the Antarctic form?, Eos, 97, doi:10.1029/2016EO055673. Published on 12 July 2016.

https://eos.org/research-spotlights/how-do-the-deep-waters-of-the-antarctic-form

Extract: "For many, Antarctica is out of sight, out of mind. However, the waters that surround the landmass play a major role in the global climate.
The Southern Ocean absorbs and stores a high amount of carbon dioxide, acting as a buffer to slow the rate of climate change. The way these waters form and circulate in the deepest reaches of the ocean is an important control on the ability of these waters to store carbon and act as a climate safeguard.



The researchers found that both glacial ice and sea ice govern gas concentrations in these deep water masses. It was already known that salty brine rejection during sea ice formation around Antarctica dramatically alters the density of these deepest waters. This study demonstrates that the same is true for gas concentrations.

The noble gas content found in bottom water, the scientists found, tells a story specific to how this water formed and where it traveled. After it leaves the surface, the water picks up a small fraction of ice melt from glaciers, icebergs, and ice shelves, which further modifies the water’s noble gas concentrations, forming a unique “fingerprint.” Using such fingerprints collected across space and time, it may be possible to reconstruct glacial melt and sea ice production in the past, including during the last major ice age, when ocean properties were distinct from today."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson