Arguments
Is Antarctica losing or gaining ice?
What the science says...
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Antarctic sea ice is gaining sea ice but Antarctica is losing land ice at an accelerating rate, which has implications for sea level rise. |
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Climate Myth...
Antarctica is gaining ice
"[Ice] is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap." (Greg Roberts, The Australian)
Arguments that we needn't worry about loss of ice in the Antarctic because sea ice is growing or even that sea ice in the Antarctic disproves that global warming is a real concern hinge on confusion about differences between sea and land ice, and what our best information about Antarctic ice tells us.
As well, the trend in Antarctic sea ice is not a permanent feature, as we'll see. But let's look at the main issues first.
- Sea ice doesn't play a role in sea level rise or fall.
- Melting land ice contributes to sea level rise.
- The net, total behavior of all ice in the Antarctic is causing a significant and accelerating rise in sea level.
Antarctic sea ice is ice which forms in salt water mostly during winter months. When sea ice melts, sea level does not change.
Antarctic land ice is the ice which has accumulated over thousands of years in Antarctica by snowfall. This land ice is stored ocean water that once fell as precipitation. When this ice melts, the resulting water returns to the ocean, raising sea level.
What's up with Antarctic sea ice?
At both poles, sea ice grows and shrinks on an annual basis. While the maximum amount of cover varies from year to year, there is no effect on sea level due to this cyclic process.
Figure 1: Coverage of sea ice in both the Arctic (Top) and Antarctica (Bottom) for both summer minimums and winter maximums. Source: National Snow and Ice Data Center
Trends in Antarctic sea ice are easily deceptive. For many years, Antarctic sea was increasing overall, but that shows signs of changing as ice extent has sharply declined more recently. Meanwhile, what's the relationship of sea ice to our activities? Ironically, plausible reasons for change may be of our own making:
- Ozone levels over Antarctica have dropped causing stratospheric cooling and increasing winds which lead to more areas of open water that can be frozen (Gillett & Thompson 2003, Thompson & Solomon 2002, Turner et al. 2009).
- The Southern Ocean is freshening because of increased rain and snowfall as well as an increase in meltwater coming from the edges of Antarctica's land ice (Zhang 2007, Bintanja et al. 2013). Together, these change the composition of the different layers in the ocean there causing less mixing between warm and cold layers and thus less melted sea and coastal land ice.
Against those factors, we continue to search for final answers to why certain areas of Antarctic sea ice grew over the past few decades (Turner et al, 2015).
More lately, sea ice in southern latitudes has shown a precipitous year-on-year decline (Parkinson, 2019). While there's a remaining net increase in annual high point sea ice, the total increase has been sharply reduced and continues to decline.
How is Antarctic land ice doing?
We've seen that Antarctic sea ice is irrelevant to the main problem we're facing with overall loss of ice in the Antarctic: rising sea level. That leaves land ice to consider.
Figure 2: Total Antarctic land ice changes and approximate sea level contributions using a combination of different measurement techniques (IMBIE, 2017). Shaded areas represent measurement uncertainty.
Estimates of recent changes in Antarctic land ice (Figure 2) show an increasing contribution to sea level. Between 1992 and 2017, the Antarctic Ice Sheets overall lost 2,720 giga-tonnes (Gt) or 2,720,000,000,000 tonnes into the oceans, at an average rate of 108 Gt per year (Gt/yr). Because a reduction in mass of 360 Gt/year represents an annual global-average sea level rise of 1 mm, these estimates equate to an increase in global-average sea levels by 0.3 mm/yr.
There is variation between regions within Antarctica as can be seen in Figure 2. The West Antarctic Ice Sheet and the Antarctic Peninsula Ice Sheet are losing a lot of ice mass, at an overall increasing rate. The East Antarctic Ice Sheet has grown slightly over the period shown. The net result is a massive loss of ice.
Takeaway
Independent data from multiple measurement techniques (explained here) show the same thing: Antarctica is losing land ice as a whole and these losses are accelerating. Meanwhile, Antarctic sea ice is irrelevant to what's important about Antarctic ice in general.
Basic rebuttal written by mattking
Update July 2015:
Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 31 January 2020 by BaerbelW . View Archives
Eclectic @525,
I don't think it is correct to say that Swally's Antarctic ice loss hypothesis is "now obsolete." It is glaceologists conundrum which implies a level of ice loss from Antarctic Ice Sheets that are certainly outside the levels calculated by more conventional methods, thus an "outlier." But surely the conundrum has yet to be resolved, thus Zwally et al (2021).
My apologies, MA Rodger, for using the word "obsolete" , in describing the Zwally 2015 paper. I am guilty of achieving more brevity than wit.
And thank you for the Zwally (et al.) 2021 paper , illustrating the academic bun-fight re mass balance (too many buns for me to wish to digest).
However, it was amusing to see his wording: "... disparate estimates [of about 100 Gigatonnes per annum] of the [East Antarctic] mass balance have not been properly resolved."
Overall, my suspicious mind detected a whiff of rear-guard justification, with Zwally attempting to juggle isostatic changes / altimetric measurements / gravimetric measurements.
For me, the take-home message from all the Antarctic studies, is that the totality of the ice-sheet is in approximate stasis (plus or minus a few decades). And most importantly, Antarctica supplies no support for science-denialists who wish to claim that the south polar situation disproves the mainstream climate science.
[ Note to Moderator ]
Strangely, the post #526 by MA Rodger has been jumped from page 21 (which would normally host 50 comments) onto a new page [22].
Is the SkS long-suffering volunteer coder able to correct this? And if I may also point out ~ clicking on the latest comment for this thread (in the standard heading comments section) produces a jump to page 11, rather than to the latest page.
[ Note to Moderator ]
I must take back part of my above comment ~ I see on other threads that each page of comments holds only 25 comments. Must have been dozing at my keyboard all this time . . . I had remembered 50 comments as the standard size page.
Nevertheless, can the coding be altered to deliver the latest page, when clicking on the latest comment on the general Comments section? Thanks.
[BL] What's the difference between 25 and 50, between friends?
I, too, have noticed the odd behaviour of following links from the Recent Comments page to the long comments sections of some blog posts. In this case, clicking on your most recent post gets me to page 11 (claiming to be out of 20), when your post is actually on page 22. I need to go to page 13 or later before page 22 is listed as an option.
I'll bring this to the attention of our more technical volunteers.
Thank you , Bob.
A coffee + diligent searching, has shown me that not all SkS pages rollover at just 25 comments. But your calm philosophical attitude points me toward taking a more relaxed view of this "existential" threat posed by page irregularities. (When did existential become the must-use word for all politicians' discussions? )
Oh, and please consider deleting all these off-topic comments here.
Thanks, BL.