Antarctic Sea Ice Extent

[LithiaWx]

If Antarctica gaining 5% extra ice volume is unprecedented.

What do you call the Arctic losing 70-80% of it's ice volume?

 

This is a thread about Antarctica. I have made my views on the state of the arctic ice very clear in the thread dedicated to the Arctic ice. 

[Isotherm]

Red herring. You're changing the subject.

 

 

 

If Antarctica gaining 5% extra ice volume is unprecedented.

What do you call the Arctic losing 70-80% of it's ice volume?

[CAD_Wedge_NC]

If Antarctica gaining 5% extra ice volume is unprecedented.

What do you call the Arctic losing 70-80% of it's ice volume?

 

  The mean extent is about 18.5 million. We are at 20.1 million. That's 1.6 million above average. Add that to our current Arctic sea ice extent and you are back to the 1979-2000 average. So, I say again.... bi-polar seesaw.

  I don't see your point. Global sea ice levels are remaining near normal.

[superjames1992]

Designed by fate, retribution for humanity's enslavement of the Earth.

 

Thom Hartmann

 

"Tipping points could be years, decades, or centuries down the road. The big danger is that you can only recognize them when it is too late to do anything about it"

 

Wha.........? 

[Jonger]

Wha.........? 

 

Fossil fuels extended our lifespan, ended slavery, ushered in the space age, granted us technological advancements that will springboard human knowledge for eternity... but.... We will all burn in hell for it in the end.

 

Am I right?

 

[LithiaWx]

 

 

Unprecedented in the satellite era

[stadiumwave]

Figure5.png

 

S_stddev_timeseries.png

 

Unprecedented in the satellite era

 

 

The climb is probably over

[FPizz]

That is really impressive

[chubbs]

This modeling study shows that increased Antarctic ice shelf melting and glacier discharge can be a negative feedback causing sea ice expansion and cooling the open water surrounding the sea ice. 

 

Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion

·        R. Bintanja, G. J. van Oldenborgh,  S. S. Drijfhout, B. Wouters & C. A. Katsman

Nature Geoscience 6, 376–379 (2013) 

doi:10.1038/ngeo1767

 

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 expanded¹, with record extent² in 2010. This ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling³. 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 trends⁴, 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.

[GaWx]

I have asked here several times if the increased ice down there would cause cooling and, therefore, a negative feedback to AGW down there. This paper sounds like it is saying something similar. Hmmm, food for thought regarding the complexities and the idea of negative feedbacks quite possibly counteracting AGW.

Opinions? Am I looking at this idea of negative feedbacks correctly?

[chubbs]

I have asked here several times if the increased ice down there would cause cooling and, therefore, a negative feedback to AGW down there. This paper sounds like it is saying something similar. Hmmm, food for thought regarding the complexities and the idea of negative feedbacks quite possibly counteracting AGW.

Opinions? Am I looking at this idea of negative feedbacks correctly?

Increased sea ice is a strong negative feedback along with ice sheet melting. If this paper is correct then AGW could cause local surface cooling near Antarctica while deeper waters are warming

[Sundog]

Fossil fuels extended our lifespan, ended slavery, ushered in the space age, granted us technological advancements that will springboard human knowledge for eternity... but.... We will all burn in hell for it in the end.

Am I right?

or.jpg

That's like saying dumping sludge into rivers and polluting groundwater is the reason we have modern technology. We don't need to do those things in order to achieve better standards of living.

We don't need to pollute in order to have all this tech, especially not anymore. So just because it happened in the past doesn't mean it has to continue perpetually.

[bluewave]

This modeling study shows that increased Antarctic ice shelf melting and glacier discharge can be a negative feedback causing sea ice expansion and cooling the open water surrounding the sea ice. 

 

 

 

Interesting comparison to Greenland in the Supplementary information.

 

http://www.nature.com/ngeo/journal/v6/n5/extref/ngeo1767-s1.pdf

 

 

Does the same mechanism play a role around Greenland?

There may exist a Northern Hemisphere analogue of the mechanism put forward in  this paper, as indicated by positive autumn sea ice trends and cooler SSTs directly  adjacent to the Greenland coast (Supplementary Figure 11). These are possibly  associated with significantly increased summer surface melt and runoff from the  Greenland ice sheet (van den Broeke et al., 2009). This northern variant of the

proposed mechanism may be sufficiently strong to locally and seasonally offset the  strong and accelerating Arctic warming and sea ice retreat, even though the area of  influence is restricted to the waters directly adjacent to Greenland. It must be noted,  though, that other processes may also contribute to increased sea ice around

 Greenland, such as enhanced southward sea ice transport through Fram Strait. However, no conclusive long-term trend in Fram Strait ice transport has been found 161 (Smedsrud et al., 2008).

[csnavywx]

I have asked here several times if the increased ice down there would cause cooling and, therefore, a negative feedback to AGW down there. This paper sounds like it is saying something similar. Hmmm, food for thought regarding the complexities and the idea of negative feedbacks quite possibly counteracting AGW.

Opinions? Am I looking at this idea of negative feedbacks correctly?

I think you are on the right track, at least in terms of surface SST cooling in the Southern Ocean and perhaps the North Atlantic (closer to Greenland). Hansen and Sato even explored this possibility, coining it the "iceberg cooling effect". The key is that the increase in ice a symptom (and possibly a slight assisting feedback) not the root cause of the cooling.

 

 

 

In particular, the lower the stability of the ice sheets (especially the WAIS), the higher the base sensitivity to CO2 (and thus steeper SLR), the stronger this negative feedback becomes (at least until enough ice melts WAY down the road).

 

Warm, salty water is shunted underneath this cooler/fresher layer and partially entrained into the circumpolar deep water (CDW) surrounding Antarctica, which is already relatively warm. Stronger westerly wind stress at the surface via a strengthened PV  helps drive CDW onto the shelves in the Amundsen sector, which has already helped accelerate melting in that region. A cooler Southern Ocean is almost sure to amplify that mechanism as the tropics continue to warm.

 

Edited to include the cause of the increase in westerly wind stress.

[Sophisticated Skeptic]

I see a lot of little facts thrown around here and there....but any strong consensus / universal agreement on why such record high ice cover in Antaractica ? 

[bluewave]

I see a lot of little facts thrown around here and there....but any strong consensus / universal agreement on why such record high ice cover in Antaractica ? 

 

http://www.scar.org/2014/602-increase-in-antarctic-sea-ice-observed

 

“This is not unexpected,” said Nathan Kurtz, a cryospheric scientist at NASA Goddard. He noted that many climate models actually predict a short-term increase in Antarctic sea ice. Factors like increasing fresh water and higher wind speeds promote ice growth and expansion—factors that appear to be dominating right now. In the long-term, Kurtz added, “increasing near-surface air temperatures are expected to have the stronger effect and begin to melt the ice and halt the expansion.”

[AvantHiatus]

Ice-melt is bad news in the long-haul even with negative feedbacks. Not to mention it creates insane thermal gradients if those projections are accurate, leading to massive oceanic storms.

[StudentOfClimatology]

Increased sea ice is a strong negative feedback along with ice sheet melting. If this paper is correct then AGW could cause local surface cooling near Antarctica while deeper waters are warming

Okay, but we have yet to observe any large scale warming down there, so that's not the forcing responsible. The primary mechanism appears to be a strengthening +SAM due to O^3 depletion, which is temporarily counteracting AGW forcing.

Note that while the AAO has been increasing, temps have been flat, suggesting that the underlying AGW warming is occurring, but is being masked by the stronger PV.

[chubbs]

Okay, but we have yet to observe any large scale warming down there, so that's not the forcing responsible. The primary mechanism appears to be a strengthening +SAM due to O^3 depletion, which is temporarily counteracting AGW forcing.

Note that while the AAO has been increasing, temps have been flat, suggesting that the underlying AGW warming is occurring, but is being masked by the stronger PV.

 

As described in the link below warmer sea water at depth is melting the underside of floating ice shelves allowing increased glacier discharge. Not discounting stronger PV and other factors. Need more work to sort out relative importance of different mechanisms.

 

http://climate.nasa.gov/news/937/

[StudentOfClimatology]

As described in the link below warmer sea water at depth is melting the underside of floating ice shelves allowing increased glacier discharge. Not discounting stronger PV and other factors. Need more work to sort out relative importance of different mechanisms.

http://climate.nasa.gov/news/937/

That's an old, debunked theory...looks like NASA needs to read the latest literature on this topic.

The OHC a warming is only statistically detectable below 50m. Any deep-ice melt would cool OHC in that domain, and it would be maximized at depth..not at the surface. That is not what we observe. Instead we have a surface-maximized cooling, suggesting stronger winds associated with a stronger circumpolar vortex.

[chubbs]

That's an old, debunked theory...looks like NASA needs to read the latest literature on this topic.

The OHC a warming is only statistically detectable below 50m. Any deep-ice melt would cool OHC in that domain, and it would be maximized at depth..not at the surface. That is not what we observe. Instead we have a surface-maximized cooling, suggesting stronger winds associated with a stronger circumpolar vortex.

Theory? The NASA site describes new data showing that 55% of ice shelf mass loss is from bottom melt. Note a surface maximized cooling is exactly what the paper I posted above obtained due to reduced mixing with warmer waters below. 

[DTWXRISK]

great call last  year on the record  warm   winter  of the central and eastern US

 

If Antarctica gaining 5% extra ice volume is unprecedented.

What do you call the Arctic losing 70-80% of it's ice volume?

[StudentOfClimatology]

Theory? The NASA site describes new data showing that 55% of ice shelf mass loss is from bottom melt. Note a surface maximized cooling is exactly what the paper I posted above obtained due to reduced mixing with warmer waters below.

Problem is, that NASA article appears to be wrong. Whoever wrote it and/or the supposed study is either not well versed in ocean dynamics or has not read the latest literature on the topic. A large majority of the article is just pure BS, sorry.

(1) Reducing vertical mixing would warm SSTs and cool the deep oceans, not visa versa. Suggesting otherwise makes no logical sense based on energy flow alone.

(2) There has been a net cooling of the Southern Ocean above ~50m in depth. Any bottom melt at or below that depth will lead to a maximized cooling in that specific domain and below, not at the sea surface...basic thermodynamics. Diffusion will dampen the anomaly away from the source of the melt.

Meanwhile, we *have* observed stronger winds, a stronger circumpolar vortex, and a cooling of the top 50m of the Southern Ocean. Kind of speaks for itself.

[mitchnick]

http://www.scar.org/2014/602-increase-in-antarctic-sea-ice-observed

 

“This is not unexpected,” said Nathan Kurtz, a cryospheric scientist at NASA Goddard. He noted that many climate models actually predict a short-term increase in Antarctic sea ice. Factors like increasing fresh water and higher wind speeds promote ice growth and expansion—factors that appear to be dominating right now. In the long-term, Kurtz added, “increasing near-surface air temperatures are expected to have the stronger effect and begin to melt the ice and halt the expansion.”

What models and how about some links to prove they did? (not you Bluewave, from the Kurtz)

It sure seems like whenever something occurs that goes against the AGW theorists, they always sit back and say "well, this was expected/predicted" and so it means nothing.

And what does he mean "in the long term" and how strong an effect? When does the ice "begin to melt and halt the expansion."

Maybe it's me, but these scientists sound far too cavalier in my book.

[chubbs]

Problem is, that NASA article appears to be wrong. Whoever wrote it and/or the supposed study is either not well versed in ocean dynamics or has not read the latest literature on the topic. A large majority of the article is just pure BS, sorry.

(1) Reducing vertical mixing would warm SSTs and cool the deep oceans, not visa versa. Suggesting otherwise makes no logical sense based on energy flow alone.

(2) There has been a net cooling of the Southern Ocean above ~50m in depth. Any bottom melt at or below that depth will lead to a maximized cooling in that specific domain and below, not at the sea surface...basic thermodynamics. Diffusion will dampen the anomaly away from the source of the melt.

Meanwhile, we *have* observed stronger winds, a stronger circumpolar vortex, and a cooling of the top 50m of the Southern Ocean. Kind of speaks for itself.

Comments:

 

1) Not near Antarctica where air is colder than water particularly in winter

 

2) This pattern is exactly as modeled in the paper I posted. Here is a quote from the supplemental "Because of the reduced mixing with warmer waters below, as per our hypothesis, the surface waters cool as shown by reduced SST's in exactly the 

regions of surface freshening"

 

The strengthening polar vortex also plays an important role. Both mechanisms are working in tandem.

[Jonger]

Antarctica hasn't shown any significant warming, so any mechanism used to describe increasing sea ice involving melting land ice, should be tossed.

It sounds like a desperate attempt to throw a wet blanket on increasing sea ice. Antarctica has been losing mass since before we started monitoring it.

[bluewave]

What models and how about some links to prove they did? (not you Bluewave, from the Kurtz)

It sure seems like whenever something occurs that goes against the AGW theorists, they always sit back and say "well, this was expected/predicted" and so it means nothing.

And what does he mean "in the long term" and how strong an effect? When does the ice "begin to melt and halt the expansion."

Maybe it's me, but these scientists sound far too cavalier in my book.

 

This study was done in 2006. While increasing Antarctic sea ice is an interesting phenomenon, it's the

potential land glacier melt contribution to sea level rise in future centuries that is the main concern with Antarctica.

 

 

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions

 

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

 

 

To investigate the seeming paradox of increasing Antarctic sea ice and increasing atmospheric and oce- anic temperatures for the Southern Ocean during 1979– 2004, a global POIM that includes a POP ocean model and a multicategory TED sea ice model was forced by the NCEP–NCAR reanalysis data that include increas- ing SAT, SDLR, and P and decreasing SDSR. There are many uncertainties with both the model and the reanalysis data, and the results must be viewed with caution. Driven by the reanalysis forcing, the model simulates an increase of 0.20 1012 m3 yr1 (1.0% yr1) in total Antarctic sea ice volume and 0.084 1012 m2 yr1 (0.6% yr1) in sea ice extent from 1979 to 2004, whereas the satellite observations show an increase of 0.027 1012 m2 yr1 (0.2% yr1) in sea ice extent dur- ing the same period (Figs. 2d and 5a; Table 1). When snow–ice formation is parameterized in the model, the simulated positive trend is even larger. This indicates that it is possible for the Antarctic sea ice to increase significantly in warming atmospheric conditions.

The nature of the phenomenon of increasing Antarc- tic sea ice in a warming environment may be explained by the following (Fig. 10). When SAT/SDLR increases, the upper-ocean temperature increases (which causes SAT to increase concurrently through air–sea interac- tions) and ice growth decreases, leading to a decrease in salt rejection from the new ice and therefore in the

[StudentOfClimatology]

Comments:

1) Not near Antarctica where air is colder than water particularly in winter

2) This pattern is exactly as modeled in the paper I posted. Here is a quote from the supplemental "Because of the reduced mixing with warmer waters below, as per our hypothesis, the surface waters cool as shown by reduced SST's in exactly the

regions of surface freshening"

The strengthening polar vortex also plays an important role. Both mechanisms are working in tandem.

The paper is BS and is refuted by observations.

1) This is only true for a small portion of the Southern Ocean, and only during June-July. Insolation is far greater than the typical ocean-skin thermals down there, through depth. Do I have to explain the energy flow-budget of the Southern Ocean domain? Should be pretty basic research.

2) This is BS. Observations depict an INCREASE in vertical mixing, not a decrease...as winds have strengthened substantially over the Southern Ocean since the mid 1980s, invigorating vertical overturning. Furthermore, how does ice-melt at-depth lead to a warming of those waters and a cooling of the SSTs? Assuming the waters are warming at-depth, the laws of thermodynamics require that any cold-pooling be maximized at the source...diffusion will dilute the anomalies with-distance.

[Sundog]

great call last  year on the record  warm   winter  of the central and eastern US

 

Irrelevant. 

[The_Global_Warmer]

great call last  year on the record  warm   winter  of the central and eastern US

 

Never "predicted" that you liar.