Antarctic Sea Ice Extent

[StudentOfClimatology]

CDW-driven melt has increased considerably over the past 20 years, that's not really in doubt either. Neither is the freshening of the surface layer. Or the fact that the Weddell polynya doesn't appear anymore either.

Just FWIW, I presented the study to a few oceanographers I know at U.M.D today, just out of curiosity. They both agree the paper should not have passed peer review.

Even if the 50-75m layer was warming (observations suggest otherwise), the associated deepwater ice melt would lead to maximum cool-pooling at-depth, rather than mysteriously teleporting to the surface. Instead, we have a warming at-depth and a cooling at the sea-surface, in tandem with stronger winds and a deeper, expanding circumpolar vortex.

The case is pretty much closed here, in my view. I don't understand the need to invent pseudotheories when a rational, well supported physical mechanism is staring you right in the face.

[Sophisticated Skeptic]

A little messy at times, but a lot of interesting discussion regardless. 

 

Especially with the rates of melt on-land and off . 

 

What Antarctica looks like without the ice.   Image and Video

 

http://www.youtube.com/watch?v=usDzh7l5HZw

[chubbs]

Yep. Until you explain how bottom-melt can accelerate despite the observed cooling of the upper 50-75m of the Southern Ocean, and a notable increase in vertical mixing, I call BS.

Furthermore, how the supposed deep-water melt (below 50-75m) can magically teleport from that depth to the sea surface is still a mystery to nearly everyone I've asked about this today (including two oceanographers).

Key glaciers are grounded 1-3 km below the sea surface unaffected by surface cooling (see Table 1 of link below). This link also has the following quote "Bottom melting freshens and cools the seawater, adding buoyancy that drives upwelling as the ice shoals seaward."  

 

I should have also mentioned Increased glacier discharge. Glacier discharge is increasing as ice shelves weaken and is probably more important on a mass basis than bottom melt. It is interesting that Antarctic sea ice started to increase more rapidly after 2005 just as ice sheet mass loss was accelerating.

 

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/8560/1/02-1084.pdf?origin=publication_detail

[Sophisticated Skeptic]

I was surprised to see this piece posted earlier this year....how an under-ice volcano likely wouldn't penerate through the ice cap.  

 

http://www.dailymail.co.uk/news/article-2625583/Newly-discovered-active-volcano-erupt-underneath-ice-Antarctica-add-effects-global-warming-say-scientists.html

[StudentOfClimatology]

Key glaciers are grounded 1-3 km below the sea surface unaffected by surface cooling (see Table 1 of link below). This link also has the following quote "Bottom melting freshens and cools the seawater, adding buoyancy that drives upwelling as the ice shoals seaward."

I should have also mentioned Increased glacier discharge. Glacier discharge is increasing as ice shelves weaken and is probably more important on a mass basis than bottom melt. It is interesting that Antarctic sea ice started to increase more rapidly after 2005 just as ice sheet mass loss was accelerating.

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/8560/1/02-1084.pdf?origin=publication_detail

Exactly, which is why the theory is unable to explain the observations. We have a cooling observed from 0-75m, and a warming observed below 100m. Unless this meltwater sourced from 1-3km down has magical teleportation powers and/or can break the laws of thermodynamics, the theory is bunk. That meltwater will warm through diffusion/be dispersed the farther it gets from the ice sheet(s).

As for glacier discharge, you need warming to accerelate that. There has been no observable warming over the Antarctic domain since the satellite era began. Just let this go, please.

[nflwxman]

Exactly, which is why the theory is unable to explain the observations. We have a cooling observed from 0-75m, and a warming observed below 100m. Unless this meltwater sourced from 1-3km down has magical teleportation powers and/or can break the laws of thermodynamics, the theory is bunk. That meltwater will warm through diffusion/be dispersed the farther it gets from the ice sheet(s).

As for glacier discharge, you need warming to accerelate that. There has been no observable warming over the Antarctic domain since the satellite era began. Just let this go, please.

I'm not sure you need the laws of thermodynamics for salinity changes.  If you put clean water in a glass of salt water, the entire glass becomes a less concentrated saline solution.  And a fraction of a degree change is deep ocean waters can cause under surface bottom melting.  Not sure what you are arguing.

 

The study could be incorrect due to uncertain measurements/methodology, but the theory is technically sound.

[nflwxman]

Just FWIW, I presented the study to a few oceanographers I know at U.M.D today, just out of curiosity. They both agree the paper should not have passed peer review.

Even if the 50-75m layer was warming (observations suggest otherwise), the associated deepwater ice melt would lead to maximum cool-pooling at-depth, rather than mysteriously teleporting to the surface. Instead, we have a warming at-depth and a cooling at the sea-surface, in tandem with stronger winds and a deeper, expanding circumpolar vortex.

The case is pretty much closed here, in my view. I don't understand the need to invent pseudotheories when a rational, well supported physical mechanism is staring you right in the face.

Which oceanographers?  I know a few from UMD from my time working at the department at Rutgers.  I'd love to discuss this topic at length with them as I'm not well versed.

[StudentOfClimatology]

I'm not sure you need the laws of thermodynamics for salinity changes. If you put clean water in a glass of salt water, the entire glass becomes a less concentrated saline solution.

Exactly, through the process of diffusion and the severing of chemical bonds, which is what kills this stupid theory. The supposed melting taking place 1-3km below the sea surface will not lead to cooling at 0-75m and a warming below 100m...the meltwater anomalies will be diluted over distance via the process of diffusion.

The study could be incorrect due to uncertain measurements/methodology, but the theory is technically sound.

The theory is bunk. Have you read the paper?

[chubbs]

Exactly, which is why the theory is unable to explain the observations. We have a cooling observed from 0-75m, and a warming observed below 100m. Unless this meltwater sourced from 1-3km down has magical teleportation powers and/or can break the laws of thermodynamics, the theory is bunk. That meltwater will warm through diffusion/be dispersed the farther it gets from the ice sheet(s).

As for glacier discharge, you need warming to accerelate that. There has been no observable warming over the Antarctic domain since the satellite era began. Just let this go, please.

 Fresh water is less dense also there is no doubt that glacier discharge is increasing  

 

Sustained increase in ice discharge from the Amundsen Sea Embayment,West Antarctica, from 1973 to 2013

 

J. Mouginot1, E. Rignot1,2, and B. Scheuchl1

 

Geophysical Research Letters doi:10.1002/2013GL059069.

 

Abstract We combine measurements of ice velocity from Landsat feature tracking and satellite radar

interferometry, and ice thickness from existing compilations to document 41 years of mass flux from the

Amundsen Sea Embayment (ASE) of West Antarctica. The total ice discharge has increased by 77% since

1973. Half of the increase occurred between 2003 and 2009. Grounding-line ice speeds of Pine Island Glacier

stabilized between 2009 and 2013, following a decade of rapid acceleration, but that acceleration reached

far inland and occurred at a rate faster than predicted by advective processes. Flow speeds across Thwaites

Glacier increased rapidly after 2006, following a decade of near-stability, leading to a 33% increase in flux

between 2006 and 2013. Haynes, Smith, Pope, and Kohler Glaciers all accelerated during the entire study

period. The sustained increase in ice discharge is a possible indicator of the development of a marine ice

sheet instability in this part of Antarctica.

[StudentOfClimatology]

Fresh water is less dense also there is no doubt that glacier discharge is increasing.

Sure, but that's not going to explain either the observed ocean thermals or the slight cooling of the Antarctic as a whole. The stronger circumpolar vortex, possibly forced by anthropogenic CFC emissions, explains the observations perfectly.

Sustained increase in ice discharge from the Amundsen Sea Embayment,West Antarctica, from 1973 to 2013

J. Mouginot1, E. Rignot1,2, and B. Scheuchl1

Geophysical Research Letters doi:10.1002/2013GL059069.

That's a much better paper, but is largely irrelavent to the Antarctic as a whole, in terms of temperature measurements and observed oceanic processes.

[csnavywx]

Just FWIW, I presented the study to a few oceanographers I know at U.M.D today, just out of curiosity. They both agree the paper should not have passed peer review.

Even if the 50-75m layer was warming (observations suggest otherwise), the associated deepwater ice melt would lead to maximum cool-pooling at-depth, rather than mysteriously teleporting to the surface. Instead, we have a warming at-depth and a cooling at the sea-surface, in tandem with stronger winds and a deeper, expanding circumpolar vortex.

The case is pretty much closed here, in my view. I don't understand the need to invent pseudotheories when a rational, well supported physical mechanism is staring you right in the face.

My post was a follow-on to MarrietaWx's post further up the page. I failed to quote it.

 

Don't get me wrong. Increased precip and wind stress/mixing due to a ozone-depletion enhanced PV are still definitely driving the bus. I don't think ice sheet melt is a main driving force of freshening/cooling in the Southern Ocean, at least yet.  The greatest effect would be near the main iceberg discharge basins and limited to where those bergs can effectively reach. Later down the road, if enough CDW-driven melt ensues (and the CDW continues to warm), then it very well might become a big player, particularly if we see the WAIS continue to destabilize.

 

My point in bringing up the freshening and disappearance of the Weddell Polynya is that it appears the increased stratification due to salinity changing is shutting down some of these convectively driven and/or reinforced circulations that helped release deeper ocean heat to the atmosphere and it is now trapped and free to flow to the ice shelves.

[csnavywx]

 

 Fresh water is less dense also there is no doubt that glacier discharge is increasing  

 

Sustained increase in ice discharge from the Amundsen Sea Embayment,West Antarctica, from 1973 to 2013

 

J. Mouginot1, E. Rignot1,2, and B. Scheuchl1

 

Geophysical Research Letters doi:10.1002/2013GL059069.

 

Abstract We combine measurements of ice velocity from Landsat feature tracking and satellite radar

interferometry, and ice thickness from existing compilations to document 41 years of mass flux from the

Amundsen Sea Embayment (ASE) of West Antarctica. The total ice discharge has increased by 77% since

1973. Half of the increase occurred between 2003 and 2009. Grounding-line ice speeds of Pine Island Glacier

stabilized between 2009 and 2013, following a decade of rapid acceleration, but that acceleration reached

far inland and occurred at a rate faster than predicted by advective processes. Flow speeds across Thwaites

Glacier increased rapidly after 2006, following a decade of near-stability, leading to a 33% increase in flux

between 2006 and 2013. Haynes, Smith, Pope, and Kohler Glaciers all accelerated during the entire study

period. The sustained increase in ice discharge is a possible indicator of the development of a marine ice

sheet instability in this part of Antarctica.

 

Sort of related to this -- There appears to be a link to tropical forcing in moving CDW up the shelves and into contact with these main glaciers. ENSO seems to play a significant role here.

 

Gotta be honest, the apparent instability in this sector scares the crap out of me as far as SLR busting to the high side. Far more than Greenland anyways.

[The_Global_Warmer]

Which oceanographers?  I know a few from UMD from my time working at the department at Rutgers.  I'd love to discuss this topic at length with them as I'm not well versed.

 

 

[LithiaWx]

Wow, unprecedented and epic stuff going on down under.

 

[LithiaWx]

Awesomesauce

[SVT450R]

Robot Sub Finds Surprisingly Thick Antarctic Sea Ice

http://www.livescience.com/48880-antarctica-sea-ice-thickness-mapped.html

 

Antarctica's ice paradox has yet another puzzling layer. Not only is the amount of sea ice increasing each year, but an underwater robot now shows the ice is also much thicker than was previously thought, a new study reports.

The discovery adds to the ongoing mystery of Antarctica's expanding sea ice. According to climate models, the region's sea ice should be shrinking each year because of global warming. Instead, satellite observations show the ice is expanding, and the continent's sea ice has set new records for the past three winters. At the same time, Antarctica's ice sheet (the glacial ice on land) is melting and retreating.

Measuring sea ice thickness is a crucial step in understanding what's driving the growth of sea ice, said study co-author Ted Maksym, an oceanographer at the Woods Hole Oceanographic Institution in Massachusetts. Climate scientists need to know if the sea ice expansion also includes underwater thickening. [Album: Stunning Photos of Antarctic Ice]

 

 

"If we don't know how much ice is there is, we can't validate the models we use to understand the global climate," Maksym told Live Science. "It looks like there are significant areas of thick ice that are probably not accounted for."

The findings were published today (Nov. 24) in the journal Nature Geoscience.

Like icebergs, much of Antarctica's floating sea ice is underwater, hidden from satellites that track seasonal sea ice. And it's difficult to take direct measurements from ships or drilling, because the thickest ice is also the hardest to reach, Maksym said.

The researchers were stuck aboard an icebreaker in 20-foot-thick (6 meters) pack ice for more than a week after taking advantage of a lead, or open water, that accessed thick ice, he said. "Obviously that carried some risk, and we were stuck until the wind changed direction again," he said.

Pinging the ice

Over the last four years, the international group of researchers has mapped the bottom of sea ice with an underwater robot, or autonomous underwater vehicle (AUV), during two research cruises offshore Antarctica. The AUV can swim to a depth of about 100 feet (30 m) and has upward-looking sonar to survey the bottom of the sea ice.

The robot submarine ready for launch from an icebreaker offshore Antarctica.
Credit: Peter Kimball, WHOI

View full size image

"With the AUV, you can get under ice that is either difficult to access or difficult to drill, and in each region, we found some really thick ice, thicker than had been measured anywhere else," Maksym said.

Almost all of the sea ice that forms during the Antarctic winter melts during the summer, so scientists had assumed most of the ice never grew very thick. Previous studies suggested the ice was usually 3 to 6 feet (1 to 2 m) thick, with a few rare spots reaching up to 16 feet (5 m) in thickness. For comparison, most of the Arctic sea ice is twice as thick (6 to 9 feet, or 2 to 3 m), with some regions covered with 12 to 15 feet (4 to 5 m) of ice. [50 Amazing Facts About Antarctica]

The robot sub surveys, which were spot-checked by drilling and shipboard tests, suggest Antarctica's average ice thickness is considerably higher than previous estimates. On average, the thickness of the ice was 4.6 to 18 feet (1.4 to 5.5 m). In the three regions it surveyed, the robot sub found that deformed, thickened ice accounted for at least half of and as much as 76 percent of the total ice volume, the researchers report.

"Our study shows that we're probably missing some of this thick ice, and we need to try to account for that when we try to compare what we see in models and satellites to what we see in the field," Maksym said.

The thickest ice measured during the survey was about 65 feet (20 m) thick, in the Bellingshausen Sea, Maksym told Live Science. In the Weddell Sea, the maximum ice thickness hit more than 45 feet (14 m), and offshore of Wilkes Land, the ice was about 53 feet (16 m) thick.

Next steps

These thick, craggy floes likely wouldn't exist without the fierce winds that circle Antarctica from west to east, the researchers said. Winter storms bash up the ice, freezing and reforming the rubble into new, thicker ice. "It must have been crunched up a tremendous amount and [the floes] piled up on top of each other," Maksym said. "The ice can generate enormous amounts of force if you have these strong winds. [The wind] is like an accordion, stretching it out and squishing it back together again."

The researchers' next step is to measure how much of Antarctica's total sea ice this thick ice represents. Maksym said it could be a "reasonably significant area of the pack."

The sea ice growth around Antarctica has averaged about 1.2 percent to 1.8 percent per decade between 1979 and 2012, according to the 2013 Intergovernmental Panel on Climate Change's Fifth Assessment Report. The increases are concentrated primarily in the Ross Sea in western Antarctica. Sea ice in the nearby Bellingshausen and Amundsen seas has significantly decreased. Researchers suspect these regional differences could result from stronger winds or increased meltwater from the Antarctic ice sheet, or a combination of both factors.

[StudentOfClimatology]

I don't understand what the big mystery is. We have loads of satellite data down there. It reveals a slight cooling around the continent and a strengthening circumpolar vortex. That's more than enough to explain the slight expansion of the Antarctic ice-pack, in my opinion.

[chubbs]

New paper available for free download. Not definitive and doesn't attempt to predict the future but adds to recent body of work indicating that Antarctica is not as stable to warming as thought previously.

 

http://www.sciencedirect.com/science/article/pii/S0012821X14007961

 

Potential Antarctic Ice Sheet retreat driven by hydrofracturing and ice cliff failure

David Pollard^{, ,} ,Robert M. DeConto, Richard B. Alley

 

Abstract

 Geological data indicate that global mean sea level has fluctuated on 10³ to 10⁶ yr time scales during the last ∼25 million years, at times reaching 20 m or more above modern. If correct, this implies substantial variations in the size of the East Antarctic Ice Sheet (EAIS). However, most climate and ice sheet models have not been able to simulate significant EAIS retreat from continental size, given that atmospheric CO₂ levels were relatively low throughout this period. Here, we use a continental ice sheet model to show that mechanisms based on recent observations and analysis have the potential to resolve this model–data conflict. In response to atmospheric and ocean temperatures typical of past warm periods, floating ice shelves may be drastically reduced or removed completely by increased oceanic melting, and by hydrofracturing due to surface melt draining into crevasses. Ice at deep grounding lines may be weakened by hydrofracturing and reduced buttressing, and may fail structurally if stresses exceed the ice yield strength, producing rapid retreat. Incorporating these mechanisms in our ice-sheet model accelerates the expected collapse of the West Antarctic Ice Sheet to decadal time scales, and also causes retreat into major East Antarctic subglacial basins, producing ∼17 m global sea-level rise within a few thousand years. The mechanisms are highly parameterized and should be tested by further process studies. But if accurate, they offer one explanation for past sea-level high stands, and suggest that Antarctica may be more vulnerable to warm climates than in most previous studies.

[Coach McGuirk]

[AvantHiatus]

The West Antarctic ice sheet (WAIS) has warmed by more than 0.1 °C/decade in the last 50 years, and the warming is the strongest in winter and spring. Although this is partly offset by fall cooling in East Antarctica, this effect was restricted to the 1980s and 1990s. The continent-wide average surface temperature trend of Antarctica is positive and statistically significant at >0.05 °C/decade since 1957.^[21] This warming of WAIS is strongest in the Antarctic Peninsula. In 2012, the temperature records for the ice sheet were reanalyzed with a conclusion that since 1958, the West Antarctic ice sheet had warmed by 2.4 °C, almost double the previous estimate. Some scientists now fear that the WAIS could now collapse like the Larsen B Ice Shelf did in 2002.^[22]

[chubbs]

This recent paleo study shows that- E Antarctic Ice Sheet (EAIS) retreated and advanced several times during the early Pliocene warm period as suggested by the modeling study posted above., More evidence that EAIS is vulnerable to a warming.climate

 

http://www.sciencedirect.com/science/article/pii/S0031018215000103

[Snowstorms]

Anybody here have any archives for the Antarctic sea ice? I'm looking for daily or monthly images if possible. Thanks! 

[AvantHiatus]

 

[SVT450R]

Anybody here have any archives for the Antarctic sea ice? I'm looking for daily or monthly images if possible. Thanks! 

Here are a few links problem is we don't have an abundance of data for Antarctica as compared to the arctic.

http://arctic.atmos.uiuc.edu/cryosphere/

 

http://www.iup.uni-bremen.de:8084/ssmis/index.html

 

http://nsidc.org/data/seaice_index/

[Snowstorms]

^^Awesome. Thanks for the links guys. I was trying to find daily images of the ice sheet in Antarctica, like the ones for the Arctic on cryosphere, but i couldn't find it. I guess those links will do. 

 

One of my buddies is currently doing climatology or climate science in University, so he asked me for some links on the Antarctic sea ice. 

[chubbs]

^^Awesome. Thanks for the links guys. I was trying to find daily images of the ice sheet in Antarctica, like the ones for the Arctic on cryosphere, but i couldn't find it. I guess those links will do. 

 

One of my buddies is currently doing climatology or climate science in University, so he asked me for some links on the Antarctic sea ice. 

 Daily maps plus other info at this site

 

http://www.cawcr.gov.au/staff/preid/seaice/

[AvantHiatus]

Brief Communication: Newly developing rift in Larsen C Ice Shelf presents significant risk to stability

http://www.the-cryosphere-discuss.net/9/861/2015/tcd-9-861-2015.pdf

 

Abstract

 

An established rift in the Larsen C Ice Shelf, formerly constrained by a suture zone containing marine ice, grew rapidly during 2014 and is likely in the near future to generate the largest calving event since the 1980s and result in a new minimum area for the ice shelf. Here we investigate the recent development of the rift, quantify the projected calving event and, using a numerical model, assess its likely impact on ice shelf stability. We find that the ice front is at risk of becoming unstable when the anticipated calving event occurs

 

3.1 Rift evolution and predicted calving                                                                                                                                                       The rift first crossed the Joerg Peninsula suture zone in 2012 and progressed modestly during 2013 into a region which previously appeared to resist transverse fractures (Fig. 2). The rate of rift propagation increased dramatically sometime between January and August 2014, crossing the entire Trail Inlet flow unit (∼ 20 km) in just 8 months. We do not have observations within this time period so we cannot say whether the 15 rift propagation during this time period was uniform or was very rapid for only a short part of it. Between August 2014 and late January 2015, the rift increased in length at a steady rate of ∼ 2.5 km yr−1 . From the start of our measurements the width of the rift at the 2010 rift tip position has increased at a more uniform rate than the length, and is still growing at a rate of ∼ 40 m yr−1 (Fig. 2). The area of Larsen C Ice Shelf after the proposed calving event will be 4600 km2 20 less than at present for Scenario I, and 6400 km2 less for Scenario II (Fig. 1). This amounts to potential area losses of 9 and 12 %, respectively.

Conclusions

 

We have investigated a newly developing rift in the south of Larsen C Ice Shelf which has propagated beyond its neighbours in 2013, and grew very rapidly in 2014. It seems inevitable that this rift will lead to a major calving event which will remove between 9 and 867TCD 9, 861–872, 2015 Newly developing rift in Larsen C Ice Shelf presents significant risk to stability D. Jansen et al. Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 12 % of the ice shelf area and leave the ice front at its most retreated observed position. More significantly, our model shows that the remaining ice may be unstable. The Larsen C Ice Shelf may be following the example of its previous neighbour, Larsen B, which collapsed in 2002 following similar events. 5 Acknowledgements. This work was carried out as part of the MIDAS project funded by NERC (NE/L005409/1) and continues work carried out under the NERC SOLIS project (NE/E012914/1). D. Jansen was funded by the HGF junior research group “The effect of deformation mechanism for ice sheet dynamics” (VHNG 802). We are indebted to NASA for the MODIS and Landsat data. D. Jansen would like to thank C. Wesche for helpful discussions.

 

 

[Cheeznado]

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2388.html

[dabize]

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2388.html

 

You beat me to it.

 

Looks like the East Antarctica Ice Sheet is joining the WAIS on the banana peel to the tune of another 11 feet of SLR.

 

Climate Crocks has a good post on it.

 

http://climatecrocks.com/2015/03/17/warm-oceans-wearing-away-antarcticas-plug/#more-23035

[chrisf97212]

You beat me to it.

 

Looks like the East Antarctica Ice Sheet is joining the WAIS on the banana peel to the tune of another 11 feet of SLR.

 

Climate Crocks has a good post on it.

 

http://climatecrocks.com/2015/03/17/warm-oceans-wearing-away-antarcticas-plug/#more-23035

 

LOL "when the bottom of the world loses vast amounts of ice, those of us living closer to its top get more sea level rise than the rest of the planet, thanks to the law of gravity."