Support the Arctic Sea Ice Forum and Blog

Author Topic: What's new in Antarctica ?  (Read 102366 times)

lurkalot

  • ASIF Lurker
  • Posts: 17
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #350 on: May 24, 2018, 09:14:32 PM »
Giant canyons found in trans-antarctic mountains:
http://www.bbc.co.uk/news/science-environment-44245893

Susan Anderson

  • ASIF Citizen
  • Posts: 425
    • View Profile
  • Liked: 27
  • Likes Given: 127
Re: What's new in Antarctica ?
« Reply #351 on: May 29, 2018, 05:28:16 PM »

Susan Anderson

  • ASIF Citizen
  • Posts: 425
    • View Profile
  • Liked: 27
  • Likes Given: 127
Re: What's new in Antarctica ?
« Reply #352 on: June 06, 2018, 04:44:56 AM »
from Earth Observatory, 6 June 2018: https://earthobservatory.nasa.gov/IOTD/view.php?id=92238&src=eoa-iotd
End of the Journey for Iceberg B-15Z?



Quote
When astronauts aboard the International Space Station shot this photograph on May 22, 2018, B-15Z measured 10 nautical miles long and 5 nautical miles wide. That’s still well within the trackable size. But the iceberg may not be tracked much longer if it splinters into smaller pieces. A large fracture is visible along the center of the berg, and smaller pieces are splintering off from the edges.



[Note: The original presents more information in a different order.]

Yuha

  • ASIF Citizen
  • Posts: 232
    • View Profile
  • Liked: 5
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #353 on: June 07, 2018, 04:26:49 PM »
from Earth Observatory, 6 June 2018: https://earthobservatory.nasa.gov/IOTD/view.php?id=92238&src=eoa-iotd
End of the Journey for Iceberg B-15Z?

Still visible on worldview on June 4: https://go.nasa.gov/2JohX6Q
It has split along the fracture.

Next day it is barely visible through the clouds, but it is still high enough to cause ripples in the clouds.

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 706
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #354 on: June 13, 2018, 08:10:37 PM »
Ice loss from Antarctica increased from circa 55 Gt/yr to circa 187 Gt/yr over past 25 years, according to:

Shepherd et al 2018, Mass balance of the Antarctic Ice Sheet from 1992 to 2017:
https://www.nature.com/articles/s41586-018-0179-y

Abstract
The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain.

Susan Anderson

  • ASIF Citizen
  • Posts: 425
    • View Profile
  • Liked: 27
  • Likes Given: 127
Re: What's new in Antarctica ?
« Reply #355 on: June 13, 2018, 08:17:00 PM »
I see this is a report on the (recently posted) original material from Lennart van der Linde, but will put it in anyway.

Antarctic ice loss has tripled in a decade. If that continues we are in serious trouble.
https://www.washingtonpost.com/news/energy-environment/wp/2018/06/13/antarctic-ice-loss-has-tripled-in-a-decade-if-that-continues-we-are-in-serious-trouble/

From Chris Mooney at Washington Post, this is not a primary source.

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #356 on: June 13, 2018, 10:32:22 PM »
I attach fig 2 and table 1 from the IMBIE paper. Comparing 1992-1997 to 2012-2017 shouw the mass loss rate tripling for WAIS and more than quadrupling for the peninsula.

That  issue of Nature has many good papers on Antarctica. It will take me a while to go thru them all.

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #357 on: June 16, 2018, 07:19:07 PM »
As I mentioned, the latest issue of Nature has several papers on Antarctica. I have not fully absorbed any of them yet, since i have been running around the midwest, but here are my gleanings so far.

IMBIE paper doi: 10.1038/s41586-018-0179-y

I have already posted a figure and a table previously. Here are some more excerpts, and my comments.

1)They find strong increase in overall mass loss from WAIS and the peninsula.

"At the Antarctic Peninsula, the 25-year average rate of ice-sheet mass balance is −20 ± 15 Gt/yr, with an increase of about 15 Gt/yr in losses since 2000. The strongest signal and trend has occurred in West Antarctica, where rates of mass loss increased from 53 ± 29 Gt/yr to 159 ± 26 Gt/yr between the first and final five years of our survey; the largest increase occurred during the late 2000s when ice discharge from the Amundsen Sea sector accelerated [33] . Both of these regional losses are driven by reductions in the thickness and extent of floating ice shelves, which has triggered the retreat, acceleration and drawdown of marine-terminating glaciers [34] . The least certain result is in East Antarctica, where the average 25-year mass trend is 5 ± 46 Gt/yr . Overall, the AIS lost 2,720 ± 1,390 Gt of ice between 1992 and 2017, an average rate of 109 ± 56 Gt/yr."

2) Regarding SMB, they find that there is no trend across AIS: "The temporal variability of all products is similar and they all agree on the absence of an ice-sheet-wide trend in SMB over the period 1979–2017, which implies that recent mass loss from the AIS is dominated by increased solid-ice discharge into the ocean. "

"The temporal variability of all products is similar and they all agree on the absence of an ice-sheet-wide trend in SMB over the period 1979–2017, which implies that recent mass loss from the AIS is dominated by increased solid-ice discharge into the ocean."

3) GIA uncertainties are important, and particularly so in the critical sector of Amundsen:

"Models predict the greatest rates of solid-Earth uplift (5–7 mm/yr on average) in areas where GIA is a substantial component of the regional mass change, such as the Amundsen, Ross and Filchner–Ronne sectors of West Antarctica (see Extended Data Fig. 4), but also the greatest variability (for example, a standard deviation of more than 10 mm/yr in the Amundsen sector). Away from areas with large GIA signals there is low variance among the models and broad agreement with GPS observations [45] ."

sidd






sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #358 on: June 16, 2018, 08:02:41 PM »
Another paper in this issue of Nature is a review by Shepherd et al. doi: 10.1038/s41586-018-0171-6 of the satellite record across Antarctica.

Somewhat surprisingly, they state that the overall rate of ice loss has "changed little" since 1992. I suspect they have a different definition of substantial change than I do.

"these studies show that the continent has contributed 7.6 ± 3.9 mm to global sea levels since 1992. Two-fifths (3.0 ± 0.6 mm) of this loss occurred during the past five years 10 . Although the rate of ice loss from the entire Antarctic ice sheet has changed little during the satellite record, speedup of glacier flow in the Amundsen Sea sector has led to accelerated losses from this region [37,38] ."

They note the evicence for ocean forced dynamic thinning:

"Although most of Antarctica has remained stable over the past 25 years, there are clear patterns of imbalance in many coastal sectors—such as the thickening of the Kamb Ice Stream and the thinning of glaciers flowing into the Amundsen Sea and at the Antarctic Peninsula. These changes reflect imbalance between ice flow and snow accumulation within the surrounding catchments. The pace of ice flow at the Kamb Ice Stream is unusually low [40] and has not altered in recent decades, but analysis of ice-penetrating radar measurements [41] shows that it stagnated over a century ago. Elsewhere, inland glacier thinning is almost exclusively coincident with contemporaneous ice speedup [21,42,43] (indicating that the thinning is dynamic in nature) and with perturbations at the marine termini of the glaciers [44] (indicating that the thinning has resulted from ocean forcing)."

On subglacial lakes:

"However, localized and episodic rises and falls of the ice sheet surface were then spotted in satellite interferometric [46] and altimetric records [47,48] , suggesting otherwise. These fluctuations, amounting to changes in height of 1–10 m over sub-decadal timescales, are interpreted to be the surface expressions of water transferring between active subglacial lake networks. More than a hundred active lakes have now been identified using this approach [49] ... Thanks to these data, we now know that in addition to periodically flushing subglacial cavities, the presence [52] of and fluctuations [27] in subglacial lake water can lubricate ice flow in parts of the continent."

Ice shelves: They note the majors (Ross, Ronne, Amery) are stable since the 1990s

"Although the major Ross, Filchner-Ronne, and Amery ice shelves have remained stable since the 1990s,"

That is something of a relief, I worry about Amery. (Not that i dont worry about the other two ...)

They continue:

"many ice shelves in West Antarctica have experienced long-term thinning over the same period. In the locations where retreat or thinning have occurred, the grounded ice inland has also been destabilized. The dominant control on this pattern is believed to be the presence (or absence) of warm ocean currents offshore [59] . Altogether, the volume of Antarctic ice shelves has declined through net overall thinning (166 ± 48 km^3/yr between 1994 and 2012; ref. 11 ) and through progressive calving-front retreat of those at the Antarctic Peninsula (210 ± 27 km^3/yr between 1994 and 2008; ref. 3 ). Combined, these losses amount to less than 1% of their volume. However, the highest ice shelf thinning rates have occurred in the Amundsen and Bellingshausen seas [12] , where five have lost between 10% and 18% of their thickness [11] owing to ocean-driven melting at their bases [67] ."

They briefly discuss the Larsen collapses also nd point out that thinning may not be a prerequisite for collapse:

" The relationship is, however, not universal; for example, although the Wilkins ice shelf collapsed in 2009, it did not thin in the preceding five years [79] ."

Wilkins was one of Mercer's canaries.

They discuss the speedup in glacier flows after shelves disappear leading to dynamic thinning:

"Over the past two decades, for example, surface lowering has spread inland across the drainage basins of the Pine Island and Thwaites glaciers at speeds of between 5 and 15 km/yr, and the majority of their catchments are now in a state of dynamical imbalance (they are thinning owing to accelerated flow)."

They point out reasons that the Amundsen region is vulnerable:

"Glaciers flowing into the Amundsen Sea sector of West Antarctica are particularly susceptible to climate forcing, owing to their geometrical configuration and the absence of any substantial ice shelf barrier [90] , and today the pace of ice sheet retreat along parts of this coastline dwarfs that during the Holocene period. The region’s ice shelves have thinned [11,12] by 3 to 6 m/yr, and its glacier grounding lines have retreated [85,86] by 10 to 35 km since 1992, which is 20 to 30 times the rate since the Last Glacial Maximum ..."

Ocean forcing is clearly implicated:

"The forcing for these events is now widely regarded to lie in the surrounding ocean, because ice drawdown has originated at and evolved from the terminus of neighbouring but distinct ice flow units [42], and because warm [67] and warming [44] water is present within the cavities beneath their peripheral ice shelves."

But the situation is complicated. Although

"it has been concluded [94] that the region is now undergoing marine ice sheet instability, with no geometrical obstacles to prevent irreversible decline."

there other clues that the process is not so straightforward, and doom might take it's own sweet time:

"However, satellite observations have revealed that retreat of the Pine Island Glacier halted around 2011 [95,96],and that ice thinning inland abated in the following years [88]. This suggests that the situation is more complicated than a consideration of the glacier geometry alone, and may involve changes in the degree of ocean forcing, as has occurred in the recent past [87,97] ."

Thy have an extended discussion of sea ice which i will not cover here.

In the summary:

"Although persistent ice shelves have fringed Antarctica for thousands of years 56 , there is now widespread evidence of changes in their extent [14]] and thickness [3,11] . Altogether, their volume has decreased by more than 300 km^3/yr since 1994 [3,11] , notably due to collapse and calving at the Antarctic Peninsula and rapid thinning of those in the Amundsen and Bellingshausen seas. These events have triggered retreat [85,86] and acceleration [21,43] of marine-terminating glaciers and ice streams around the continent, leading to the drawdown of ice from their inland catchments [39,42] . Since 1992, the grounded ice sheet has lost 1,350 ± 1,010 Gt of ice, causing a net 3.8 ± 2.8 mm contribution to global sea level rise [36] ."

The question remains:

"A key unanswered science question is how long it will take for the ice shelves that are currently thinning to reach a point whereby they are no longer providing effective buttressing for the grounded ice inland."

Indeed. Inquiring minds want to know, and every coastal community in the world needs to know.

I attach figs 1 and 2. They are very pretty.

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #359 on: June 16, 2018, 08:30:56 PM »
In some happier news, a letter by Shakun et al. doi: 10.1038/s41586-018-0155-6 finds that land based EAIS was stable over the last 8 Myr:

"These findings indicate that atmospheric warming during the past eight million years was insufficient to cause widespread or long-lasting meltback of the EAIS margin onto land.We suggest that variations in Antarctic ice volume in response to the range of global temperatures experienced over this period—up to 2–3 degrees Celsius above preindustrial temperatures [4] , corresponding to future scenarios involving carbon dioxide concentrations of between 400 and 500 parts per million—were instead driven mostly by the retreat of marine ice margins, in agreement with the latest models [5,6] ."

They base their conclusion on the lack of cosmogenic isotopes from ANDRILL and modelling:

"The near absence of cosmogenic nuclides in our record therefore rules out substantial and long-lasting EAIS retreat onto land during the past 8 Myr ..."

"these models suggest that warming consistent with even the most intense interglacials of the past 8 Myr would have produced minimal land exposure around the entire EAIS margin [6,8] ."

"our findings agree with model simulations which show that the terrestrial EAIS experiences minimal melt when carbon dioxide levels are at their present value of roughly 400 parts per million for extended periods of time, whereas some marine-based ice-sheet sectors largely disappear [5,23]"

ANDRILL is a gift that keeps on giving.

There are, of course, large basins of EAIS (Totten comes to mind) where ice is grounded well below present day sea level. More drilling clearly needed.

I note there are some heavy hitters on that author list. Naish must have done a lot of the modelling.

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #360 on: June 16, 2018, 08:53:12 PM »
Another letter in this issue of Nature is from Kingslake et al. doi: 10.1038/s41586-018-0208-x who see retreat and re-advance of WAIS during the last deglaciation. They analyse cores from the seafloor, ice  penetrating radar scans and models :

"Rebound-driven stabilizing processes were apparently able to halt and reverse climate-initiated ice loss. Whether these processes can reverse present-day ice loss [6] on millennial timescales will depend on bedrock topography and mantle viscosity—parameters that are difficult to measure and to incorporate into ice-sheet models."

So WAIS retreated, but then isostatic rebound elevated the previously ice covered regions sufficiently to allow the sheet to re-advance. Note that this uplift occurs over millennial timescales, so may not be important for, say, the next thousand years.

Their reconstruction (using PISM) shows that Ross and Ronne almost completely disappeared around 10KYr ago, and then the grounding lines re-advanced to present day.

"In this simulation, rising sea-level and surface temperatures during the last glacial termination drive grounding-line retreat through regions currently occupied by the Ronne and Ross ice shelves. The grounding line reaches its most retreated position around 10 thousand years (kyr) before present (bp), up to approximately  300 km inland of the present-day grounding line (Fig. 3 and Extended Data Fig. 3). Retreat exposes nearly all of our core sites and the bed of HIR to the ocean. Approximately 352,000 km 2 of the area that is covered by grounded ice today ungrounds during retreat, resulting in lithospheric rebound of up to 175 mm per year. The rising bed eventually causes the Ross and Ronne ice shelves to ground on bathymetric highs in the locations of present-day ice rises, including HIR. Ice-rise formation increases ice-shelf buttressing, causing the grounding line to re-advance towards its present-day location (Fig. 3 and Extended Data Fig. 4; Methods) "

But not so for Amundsen: "In the Amundsen Sea sector, the grounding line retreats to its modern position without substantial inland retreat and re-advance. "

The go out on a limb, i think, with this speculation:

"Furthermore, we hypothesize that the grounding line in the Weddell and Ross Sea sectors may be capable of retreating far inland of its present position without triggering runaway ice-sheet collapse."

But they do note the troubles with Amundsen:

"We note that our model does not simulate retreat and rebound driven re-advance in the Amundsen Sea sector (Fig. 3), where present-day retreat of the grounding line is causing concern about future runaway collapse 6 and recent re-advance could explain observed sub-shelf iceberg ploughmarks [28] . Our findings motivate future work to examine whether rebound-driven mechanisms could slow or reverse this retreat on millennial timescales."

I attach figure 3. They have a movie also, but i had difficulty with it, seemed to have random black patches.

sidd








sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #361 on: June 16, 2018, 09:04:43 PM »
Rintoul has a perspective and a review in this issue of Nature. The Perspective lays out an optimistic and a pessimistic scenario for AIS upto 2070. These depend on human behaviour over the next fifty years, so should be taken as an informed guess.

"Under the high-emissions scenario, Antarctica and the Southern Ocean undergo widespread and rapid change, with global consequences. But the environmental change realized by 2070 will be only a fraction of the change to which we are committed by choices made today, and the rate of change will have increased and continue to accelerate. For example, once initiated, the marine ice sheet instability will result in irreversible loss of large parts of the ice sheet resting on bedrock below sea level. Under the low-emissions scenario, in which global average temperatures remain within 2 °C of 1850 values, there is some chance that the buttressing ice shelves will survive and the Antarctic contribution to sea level rise will remain below 1 m. Under the high-emissions scenario, the ice shelves are lost and Antarctica contributes 0.6 m to 3 m of sea level rise by 2300, with an irreversible commitment [45] of 5 m to 9 m, or as much as [33] 15 m in the coming millennia."

But even in the optimistic scenario, the qualifier "there is some chance" seems to show his doubts.

The review is a magisterial analysis of local and extended dynamics of the Southern ocean.. I shall not attempt a detailed reading here, except to quote Rintoul on the uncertainties:

"The theoretical foundation for Southern Ocean dynamics is developing rapidly, but remains incomplete. This gap is reflected, for example, by the speculative nature of the above discussion of the response of the Southern Ocean to changes in forcing and by our inability to do much more than list the mechanisms that influence the delivery of ocean heat to the Antarctic margin. The fact that new observations continue to reveal surprises that challenge existing thinking also underscores gaps in knowledge; examples include the unanticipated variability of the Southern Ocean carbon sink, the dominant contribution of the Southern Hemisphere to the change in global ocean heat content in the past decade, and evidence that the East Antarctic Ice Sheet is more exposed to ocean heat transport than once thought."

Don't get me wrong. This review is required reading for an understanding of Southern ocean dynamics.

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #362 on: June 16, 2018, 09:37:56 PM »
Two other papers came to my attention, althoug not from Nature:

Bamber et al. doi: 10.1088/1748-9326/aac2f0 look at land ice contribution to sea level rise in the satellite era. Their result is smaller than many GRACE derivations, which they claim is due to smaller trends for glaciers and ice caps.

Dow et al. doi: 10.1126/sciadv.aao7212 analyse the effect of basal channelized melt on ice shelf fracture. Their principal area is Nansen but they have this to say about PIG:

"Pine Island Glacier is one of the most vulnerable regions of the Antarctic to ice shelf collapse and has seen marked thinning rates and grounding line retreat over the last decade (4, 6). Pine Island Glacier Ice Shelf has had five large calving events between 2000 and 2017. The fracture that grew to cause the most recent calving event in September 2017 initiated over one of the ice shelf basal channels. The channels have been identified from MODIS imagery (5) and radar surveys (6). A 4-km-wide polynya identified from Landsat imagery in 2000 also supports the presence of a channel in this location. The fracture (Fig. 1G) can first be seen in March 2015 with a length of 3.7 km. By February, the fracture had moved 3.4 km downstream and lengthened to 7 km. In January 2017, the fracture was 5.4 km downstream and 19 km long. This fracture culminated in a calving event in September 2017 creating the 185-km 2 B-44 iceberg. The formation of a fracture originating from the center of the ice shelf and propagating laterally, rather than from the edge toward the center has previously been attributed to crevasses originating from the grounding line (27). Here, we suggest that thinning within the basal channel is a driver for the initial transverse location of the fracture, and the role of grounding line originated crevasses is to determine the longitudinal location of fracture formation."

I attach the picture for PIG, but they have many others including Totten and Petermann.

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #363 on: June 17, 2018, 12:29:32 AM »
I seem to have omitted the Massom paper doi:10.1038/s41586-018-0212-1 on the protective effect of sea ice on ice shelves through attenuation of ocean swell. They intensively examine the Larsen and Wilkins collapses.

"A decadal-scale reduction of sea ice coverage (concentration, that is the proportion of the ocean surface covered by sea ice, and duration) over the satellite era (since 1979) in the northwestern Weddell Sea and the Bellingshausen Sea (Fig. 3; also ref. 27 ) dramatically increased the potential for substantial ocean wave energy to reach the ice shelf fronts in mid- to late summer and in early autumn. An increase in
open-water duration of approximately three months occurred between 1979/1980 and 2009/2010 [27]."

"The sea ice loss in each case resulted in extensive and sustained periods of exposure to broadly open-ocean conditions offshore "

"Occurring immediately before each disintegration event, sliver-berg calvings (Fig. 2) removed keystone blocks from the arch-like configuration of the ice shelf front that were crucial to its structural integrity."

i attach figure 3, showing decline in sea ice in the region.

sidd



oren

  • ASIF Upper Class
  • Posts: 2307
    • View Profile
  • Liked: 127
  • Likes Given: 274
Re: What's new in Antarctica ?
« Reply #364 on: June 17, 2018, 12:48:55 AM »
Thank you Sidd for all these summaries.

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #365 on: June 17, 2018, 01:32:30 AM »
I'm afraid they dont deserve to be called summaries. Consider them no more than my immediate reactions. It will take me weeks to read through them with the care they warrant.

I suggest reading at least the abstracts  for a precis of the most important results. I know I skipped a lot.

sidd

litesong

  • ASIF Citizen
  • Posts: 113
    • View Profile
  • Liked: 5
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #366 on: June 17, 2018, 09:52:18 PM »
[quote author=Lennart van der Linde link=topic=622.msg158630#msg158630  Ice loss from Antarctica increased from circa 55 Gt/yr to circa 187 Gt/yr over past 25 years, according to:
Shepherd et al 2018, Mass balance of the Antarctic Ice Sheet from 1992 to 2017:
https://www.nature.com/articles/s41586-018-0179-y
Abstract
The Antarctic Ice Sheet ......lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017..... rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. [/quote]

Meanwhile, Grace FO continues its shake down, now in a preliminary orbit:
https://www.jpl.nasa.gov/news/news.php?feature=7156
From the article:
The GRACE-FO microwave ranging instruments allow distance measurements with a precision better than one micron -- less than the diameter of a blood cell, or a tenth the width of a human hair....... To demonstrate the initial performance of GRACE-FO's microwave ranging system, the team examined its measurements of changes in the distance between the two satellites as they flew over the Himalayas...... The plot's wavy lines show how the distance between the satellites varies as the satellites pass over oceans, land areas, and particularly mountains as they orbit Earth. The observed inter-satellite distance changes, which can be as large as hundreds of microns, are in good agreement with expectations. These results give the team confidence that the mission's key microwave ranging system is performing well.
By measuring even minute changes in distance between the satellites, GRACE-FO can detect the month-to-month variations in Earth's gravity field caused by the movement of mass as small as about a half-inch (1 centimeter) of water over an area of about 200 miles (320 kilometers) in diameter.
///////
Good news, indeed!

Sleepy

  • ASIF Middle Class
  • Posts: 939
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #367 on: June 18, 2018, 05:06:58 AM »
I'm afraid they dont deserve to be called summaries. Consider them no more than my immediate reactions. It will take me weeks to read through them with the care they warrant.

I suggest reading at least the abstracts  for a precis of the most important results. I know I skipped a lot.

sidd
Thanks for your posts.
FWIW, I noticed LVDL's post on the 13th and even posted a short comment here:
https://forum.arctic-sea-ice.net/index.php/topic,428.msg158958.html#msg158958
Also saw Susan's post but none of yours, despite visiting the forum every single day.

In the past one always had the mail notifications, now one must login every single time or you loose the notifications. I don't like that, since there are some threads that I rarely comment in but do try to follow, like this one.

Why did Neven change this setting?
Omnia mirari, etiam tritissima.

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #368 on: June 18, 2018, 05:32:52 AM »
There is a link called "Show unread posts since last visit."  that shows all the threads with unseen posts.

sidd

Sleepy

  • ASIF Middle Class
  • Posts: 939
  • Every day you live, something else dies.
    • View Profile
  • Liked: 33
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #369 on: June 18, 2018, 05:42:33 AM »
Thanks, I've already worn out my scroll-wheel once. ;)
Omnia mirari, etiam tritissima.

Susan Anderson

  • ASIF Citizen
  • Posts: 425
    • View Profile
  • Liked: 27
  • Likes Given: 127
Re: What's new in Antarctica ?
« Reply #370 on: June 18, 2018, 05:42:24 PM »
Sidd, that is some outstanding review, I'm looking forward to taking a closer look when there is time. Please don't forget that I am an amateur amateur, and normally if I have something to say about ice, it is because of somebody else's work.

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #371 on: June 19, 2018, 07:17:46 AM »
More bad news. Cook in East Antarctica is more unstable than previously known:

doi: 10.5194/tc-2018-107

"We have shown that despite little change over the past decade, there have been dynamic
changes in the velocity of both the Cook East and West glaciers during periods over the past
~45 years. For Cook East we provide one of the few observations linking a short-lived increase
in velocity to a subglacial flood event, in addition to a longer-term velocity increase of 19%
between 1989 and 2001. For Cook West we link a doubling of its velocity to the near-complete
loss of its floating ice shelf between 1973 and 1989, which may have been forced by a more
variable climate in the mid-20th century"

Open access. Read all about it.

I attach fig 7

sidd

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #372 on: June 21, 2018, 10:10:33 PM »
Some good news from Antarctica: I post extracts here:

https://forum.arctic-sea-ice.net/index.php/topic,2205.msg159984/topicseen.html#msg159984

In light of this result, I suspect Kinslake et al. (on which i commented earlier) may visit to recalculate their results in the Amundsen secto, since the crust beneath is more labile than they assumed. This may help make their results in that area better.

sidd
« Last Edit: June 22, 2018, 12:04:46 AM by sidd »

litesong

  • ASIF Citizen
  • Posts: 113
    • View Profile
  • Liked: 5
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #373 on: July 06, 2018, 05:01:40 PM »
Meanwhile, Grace FO continues its shake down, now in a preliminary orbit:
https://www.jpl.nasa.gov/news/news.php?feature=7156
From the article:
To demonstrate the initial performance of GRACE-FO's microwave ranging system, the team examined its measurements of changes in the distance between the two satellites as they flew over the Himalayas...... GRACE-FO can detect the month-to-month variations in Earth's gravity field caused by the movement of mass as small as about a half-inch (1 centimeter) of water over an area of about 200 miles (320 kilometers) in diameter.
Grace-FO continues to prepare itself for accurate measurements of Earth gravity changes:
https://gracefo.jpl.nasa.gov/news/138/first-laser-light-for-grace-follow-on/
From the article:
 The LRI, which is being flown as a technology demonstration, has made its first measurements in parallel with GRACE-FO's main microwave ranging instrument, and initial comparisons of the data from the two types of instruments show that they agree as expected.
///////
Further Grace-FO alignments appear to continue the good news for Grace-FO.

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 706
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #374 on: July 16, 2018, 11:51:51 PM »
Pattyn 2018 on The paradigm shift in Antarctic ice sheet modelling:
https://www.nature.com/articles/s41467-018-05003-z

And some more on ice sheets:
https://www.nature.com/collections/vqrdvgyjdp

sidd

  • ASIF Governor
  • Posts: 3056
    • View Profile
  • Liked: 20
  • Likes Given: 0
Re: What's new in Antarctica ?
« Reply #375 on: July 17, 2018, 06:33:51 AM »
Thanx for the pointers. Nice articles.

sidd

kassy

  • ASIF Lurker
  • Posts: 5
    • View Profile
  • Liked: 4
  • Likes Given: 3
Re: What's new in Antarctica ?
« Reply #376 on: July 17, 2018, 02:12:41 PM »
Kelp and sadly also plastics can make it to Antarctica if storms help them across the ACC:

Antarctica is surrounded by the circumpolar current, an endless loop of water pushing ever-eastward, driven by the powerful southern winds and unobstructed by land, other than being forced through the narrow gap between the Antarctic Peninsula and Tierra del Fuego. Although whales and seabirds can power across this obstacle, few other life forms can do so, keeping the frozen continent almost biologically isolated from the rest of the planet.

At least that is what was believed, until the Universidad de Concepción's Dr Erasmo Macaya, unable to do the work he had come to King George Island to do, spent a lot of time walking along the beaches looking at seaweed. Macaya noticed that some of the kelp didn't look like it should be there. The oceans off Antarctica, cold as they are, do support some kelp species, but Macaya's finds were Durvillaea antarctica, which somewhat ironically does not normally live close to the continent with which it shares its name.

More details on:

http://www.iflscience.com/environment/kelp-is-undertaking-epic-voyages-to-reach-antarctica-and-we-finally-know-how/