Arguments
Is Antarctica losing or gaining ice?
What the science says...
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Antarctic sea ice extent has expanded at times but is currently (2023) low. In contrast, Antarctica is losing land ice at an accelerating rate and that has serious 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)
At a glance
Who discovered the great, South Pole-straddling continent of Antarctica? According to the National Geographic, Captain Cook came within an estimated 80 miles of it in the late 1700s, but the three first 'official' discoveries all took place in 1820 by Russian, British and American teams of seafarers respectively.
Since that initial discovery, Antarctica has attracted and inspired researchers and explorers alike. It's a challenging place, fringed by sea-ice that, unlike the Arctic, has not steadily declined but whose extent fluctuates on a seasonal basis: it's currently (February 2023) at a very low coverage, but it can and does recover from such dips. Antarctic sea-ice is no great problem, with the exception of albedo-loss in low extent years: if it all melted, it would have no effect on global sea-levels. It's the stuff on land we need to focus upon.
The land of Antarctica is a continent in two parts, divided by the 2,000 m high Transantarctic Mountains. The two parts differ in so many respects that they need to be considered separately. East Antarctica, that includes the South Pole, has the far greater landmass out of the two, some 4,000 by 2,500 kilometres in size. Although its massive ice-sheet, mostly grounded above sea level, would cause 52 metres of sea level rise if it completely melted, so far it has remained relatively stable. Snow accumulation seems to be keeping in step with any peripheral melting.
In contrast, in the absence of ice, West Antarctica would consist of islands of various sizes plus the West Antarctic Peninsula, a long mountainous arm pointing northwards towards the tip of South America. The ice sheet overlying this mixed topography is therefore grounded below sea level in many places and that's what makes it far more prone to melting as the oceans warm up. Currently, the ice-sheet is buttressed by the huge ice-shelves that surround it, extending out to sea. These slow down the glaciers that drain the ice-sheet seawards.
The risk in West Antarctica is that these shelves will break up and then there will be nothing to hold back those glaciers. This has already happened along the West Antarctic Peninsula: in 1998-2002 much of the Larsen B ice-shelf collapsed. On Western Antarctica's west coast, the ice-sheet buttressing the Thwaites Glacier – a huge body of ice with a similar surface area to the UK - is a major cause for concern. The glacier, grounded 1,000 metres below sea level, is retreating quickly. If it all melted, that would raise global sea levels by 65 centimetres.
Such processes are happening right now and may not be stoppable - they certainly will not be if our CO2 emissions continue apace. But there’s another number to consider: 615 ppm. That is the CO2 level beneath which East Antarctica’s main ice sheet behaves in a mostly stable fashion. Go above that figure and the opposite occurs - major instability. And through our emissions, we’ve gone more than a third of the way there (320 to 420 ppm) since 1965. If we don’t curb those emissions, we’ll cross that line in well under a century.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
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. However, under a high-emissions scenario, ice-loss from the East Antarctic ice-sheet is expected to be a much greater in the decades after 2100, as reported recently by Stokes et al. (2022). That’s a scenario we must avoid at all costs.
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.
Last updated on 14 February 2023 by John Mason. View Archives
bozzza
Sea ice in the SH is not relevant because the ice pack there has land under it. Whereas in the NH, i.e. the Arctic, the ice pack has sea under it.
An honest comparison between the NH and SH can only be made between the two ice packs in their entirety.
The amount of sea ice in the SH is miniscule, one might even be able to say that it is statistically zero (but I am too lazy to do the math), when compared to the size of the actual ice pack in the SH.
When the NH ice pack finally disappears, enough people will notice and we can then pass laws making those who peddled their anti-science BS liable for all the damages that their actions will have caused by introducing them to somethng called “accepting personal responsibility for their actions.”
If the SH ice pack disappears, not only will we be nationalizing 100% of the assets of those who, or whose ancestors because the proceeds of crime are still the proceeds of crime, peddled their anti-science BS to pay all the damages that their actions will have caused: We will also be stringing them up from lampposts because if the SH ice pack disappears, we are in for a world of hurt and we will seriously want to hold us some modern Nuremberg Trials.
A heat pump works by using a refrigerant but instead of the coils that radiate away the heat being outside, they are usually, in one form or another, inside.
What you call an “ocean pump” is not in fact a pump, but is a current that is part of what some call the global thermohaline circulation. Just because someone calls it a pump does not meant that a coherent and/or valid comparison can be made between it and other pumps.
A current BTW that might be in serious danger from AGW.
Also, if I were to guess, which I am about to do, my response to your final question would be along the lines of: The reason that the NH, and it’s condition, is better known then the SH’s condition is because for the past few hundred years NH countries dominated the globe, which includes said SH countries, and no one who thought that they mattered really gave a rat’s ass about the SH or anything but their own self-proclaimed superiority and/or exceptionalism.
Ok, thanks for the food for thought on pumps versus mis-nomers...
As for the last paragraph are you saying it isn't certain that the N.H. is warmer than the S.H.?
I think the other point is that summer sea ice extent is important because of its effect on albedo. Winter sea ice at either pole has little climate impact. Also relevent is the question of why is sea ice increasing/decreasing. Changing temperature in both atmosphere and ocean is important at one pole; changing winds pushing pack further out is important at the other.
(of course I read all your comments..)
Bozzza - We know a lot more about past seaice extent in NH than SH. We know temperatures at both poles are warming in recent times. Remember that the paradox with SH ice is why it is increasing despite ocean warning. (see Fig 3 in intermediate tab).
@ 404, the new scientist article was short and sweet. It talked about how cold water sank at the poles and this dragged warmer water from the equator to replace it. The way people explain things is worth noting...
Bozzza, do some reading up on the thermohaline circulation. It is driven by salinity as well as temperature and yes, it is not symmetric across hemispheres. No warm Gulf stream down here. Pretty tough for agriculture in SH below 50S whereas 50N is relatively temperate.
Bozzza
Your question was “why” is the above- the fact that the NH is warmer than the SH- not common knowledge?
I answered as honestly as I can with the knowledge I have.
To answer your revised question would first require validating the claim that the NH is in fact warmer than the SH. That is easier said than done.
Are you talking about total heat energy present north of the equator versus total heat energy south of the equator; and over what time frame. Are you talking about averages, means, or maximums versus minimums? Does all the data exist for the heat in all of the oceans in both hemispheres?
Then determining “why”, if it is true, it is not common knowledge would require an extensive analysis of all the educational systems, all the media channels, and people’s preferences and abilities when it comes finding and retaining said information. And probably a lot of other variables that I am not aware of.
bozzza - Yes, the NH is warming faster than the SH:
[Source]
This is wholly unsurprising - land warms (and cools) faster than ocean, and the SH has less land relative to ocean area (warming differential predicted by Svante Arhennius, 1896, p265). This is also partly due to Arctic amplification having an impact (shallow sea with ice surrounded by land) compared to the Antarctic (land ice surrounded by water).
What is your point?
@ 408, yeh just still haven't got my head around this thermohaline cycle yet but even more to the point I feel the basic information of the NH being warmer than the SH should be much more common knowledge than it is if we are to save the world basically... it just confuses me as to why it isn't a high priority piece of information...
@ 410, did you say the Arctic Ocean is not deep?
In trying to make sense of the whole shebang in mentally digestable chunks what effect would this have exactly?
bozzza - Average depth of the Arctic Ocean is ~1000m, while globally oceans average ~3700m, while the Southern Ocean around Antarctica averaging 4000-5000m.
bozzza - The differences in the Arctic are perhaps 1/4 the ocean thermal mass as global ocean averages, small overall size (the smallest ocean), being almost surrounded by land (which warms faster), more limited liquid interchanges due to bottlenecking than the Antarctic, and very importantly considerable susceptibility to positive albedo feedbacks; as less summer ice is present given current trends, solar energy absorbed by the Arctic ocean goes up very rapidly.
Given the land/ocean balances alone, the northern pole should warm ~10% faster than the southern.
Regarding warm/cold water exchanges, as scaddenp recommended I suggest reading up on global thermohaline circulation.
While these overall effects may not be intuitive, they are very well established.
There's an interesting time-series of models of ice thickness and other information here:
http://www7320.nrlssc.navy.mil/hycomARC/arctic.html
There's only the last 5 years of thickness represented, but it would be interesting to see a specific date animated as a gif (as opposed to the changes over a year), particularly at minimum and maximum days?
(Apologies, just realised with changing pages to create an account, I ended up posting on the Antarctic comment thread rather than the Arctic thread I was reading. However I can't see a delete comment button?)
Everyone should be happy, more sea ice means less ocean level rising. FACT.
Perhaps I'm dense, ghoward. Could you explain further? Could you also give a method that results in global net sea ice increase over a meaningful time period?
Sea ice is frozen sea water. Can you explain the mechanism behind your assertion ghoward?
"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 0.19 mm/yr."
Is my math correct in interpreting this statement to mean that it will take five years to raise sea level 1 mm and 125 years to raise sea level 1 inch? Is the 360 GT per year just from Antarctic land ice or global land ice>
renbuild1,
Your math would be correct if the rate of melt were not rising. Since the rate of melt is measured to be increasing rapidly, it will take much less than 125 years for 1 inch of melt. Recent measurements in West Antarctic indicate that the ice sheet there has passed its tippiing point. Dr. Ringot, an Antarctic and Greenland specialist and coauthor on Hansen's recent paper on sea level rise, claimed that their data indicated that the West Antarctic Ice Sheet alone would melt in decades to centuries with a sea level rise of at least 10 feet. Decades to centuries is a large range, but 10 years ago the same scientists were saying thousands of years for the sheet to melt. This melt increase will occur in a non linear manner. How much risk are you willing to take that it will not be decades?? Obviously Dr. Ringot feels it is possible or he would not have coauthored Hansen's paper. 10 feet of sea level rise would wipe out all of south and east Florida.
When processes are known to be increasing rapidly it is inappropriate to extrapolate past melt rates far into the future. Many things are hard to predict, especially the future.
The current rate of sea level rise from all sources is 3-3.5 mm/year. It is increasing. How much sea level rise is acceptable? In Tampa, Florida, where I live, we just had a flood where many homes reportedly had 2-19 inches of water inside. Since 9 inches of sea level rise has been measured in Florida, many of those homes would not have flooded without sea level rise. How much did AGW contribute to the extraordinary rain? At least some. This is damage caused today by AGW. It will only increase in the future.
renbuild1 - Geometric and exponential growth rates are not our friend here. We have to take acceleration into account.
Antarctic Ice Mass
[Source: see Fig. 10]
[Source]
Antarctic ice loss is certainly accelerating. A plot of the rate of change of mass balance from the data graphed below (two clicks down the link) perhaps is starting to show an increase in that acceleration, LINK , although it is early days for anything more than speculation.
Antarctic sea ice extent has drastically changed it's trajectory over the last 2 weeks: is there any sensible explanation for this?
bozzza @424,
The Antarctic sea ice area anomaly has gone negative in the last couple of days, the first time that has happened in four years. Prior to that (back in 2011), the SIA wobbled its way positive and negative with a long-term trend upward of 15,000 sq km pa. Seeing this recent return to negative anomalies is a return to that level of trend. It is perhaps the deviation from that long-term trend that would be easier explained, easier than the return to it.
This graph (usually 2 clicks to 'download your attachment') shows recent years of SIA up to January 2015 but doesn't really capture that long term trend. I will upload something that does when I have a moment.