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A basic overview of melting ice around the globe

Posted on 16 February 2011 by James Wight

Contrary to contrarian claims, ice is melting at accelerating rates in the Arctic, Antarctica, Greenland, and glaciers all over the world. Arctic summer sea ice has shrunk by an area equal to Western Australia, and might be all gone in a decade.

Ice sheets are beginning to shrink

An ice sheet is a huge layer of land ice. The only ice sheets are in Antarctica and Greenland.

The Greenland ice sheet is losing mass at an accelerating rate. In recent years the ice loss has spread from the south coast around to the northwest.

(Image source: Climate Signals.)

Similarly, Antarctica is also losing ice at an accelerating rate. Antarctica is basically divided into two distinct ice sheets, the West Antarctic and East Antarctic. The East Antarctic ice sheet, which is much bigger than the West Antarctic one, was until recently considered stable, but has also begun losing ice.

(Image source: NASA.)

Ice shelves are collapsing

Ice shelves are thick, floating platforms of ice formed when glaciers flow from the land onto the ocean surface.

The Antarctic Peninsula is warming rapidly. Several ice shelves have collapsed completely, including one covering 3,250 km2, almost twice the area of urban Sydney.

 

(Image source: National Snow and Ice Data Center.)

Glaciers are retreating

Glaciers are retreating around the globe. Although one can point to particular glaciers that are growing, glaciologists look for trends in the total mass of glaciers worldwide. It turns out the world’s glaciers are losing ice at an accelerating rate.

(Image data source: Cogley 2009.)

And despite all the hype about a certain mistake in the 2007 IPCC report, the Himalayan glaciers are in fact melting.

Southern sea ice not doing much

Sea ice floats on the ocean surface, and is not to be confused with ice sheets on land. Even though the Antarctic ice sheet is losing mass, the extent of sea ice around the coast of the continent has grown slightly.

This is because of a complex variety of factors, and despite the warming of the Southern Ocean. The trend is expected to reverse in coming decades as the Antarctic continues to warm.

Arctic sea ice in a death spiral?

Arctic sea ice grows and shrinks seasonally, with an annual minimum in September. In 1979, when satellites first measured it, September Arctic sea ice extent was roughly equivalent to the area of Australia. Since then it has declined by about a third, equivalent to losing Western Australia – outstripping all projections.

(Image source: Copenhagen Diagnosis.)

2010 had the third lowest minimum on record (after 2007 and 2008). Two expeditions successfully circumnavigated the Arctic Ocean in a single summer, something that would have been impossible just a few years earlier or any time in recorded history.

Contrarians claim Arctic sea ice has “recovered” since the record low extent of 2007. But sea ice exists in three dimensions, and it has continued to thin rapidly. Ice volume data paints a picture even more dire: the Arctic has actually lost not one third but two thirds of September sea ice. What’s more, the volume reached a record low in 2010 – not an encouraging sign of recovery.

2010 set the stage for continued melting. At the end of the summer, a record-breaking 86% of ice cover was less than two years old; ice older than five years has all but disappeared. The remaining new ice is thinner and much easier to melt than older ice.

 

(Image source: National Snow and Ice Data Center.)

Ice-free summers are now probably inevitable, but it’s not clear how soon because the Arctic is melting much faster than any model predicted. Mark Serreze, Director of the US National Snow and Ice Data Center, says we’re “looking at a seasonally ice-free Arctic in twenty to thirty years.” A few scientists argue that September sea ice could be essentially gone within the next decade.

This blog post is the Basic version by James Wight of the intermediate rebuttal Ice Isn't Melting.

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Comments 51 to 57 out of 57:

  1. New image of the day at Earth Observatory. 2010 was an exceptional year for Greenland’s ice cap. Melting started early and stretched later in the year than usual. Little snow fell to replenish the losses. By the end of the season, much of southern Greenland had set a new record, with melting that lasted 50 days longer than average. Also a shout out to Marco Tedesco cryocity website at CCNY, where this gem is shown: The figure above shows the standardized melting index anomaly for the period 1979 – 2010. In simple words, each bar tells us by how many standard deviations melting in a particular year was above the average. ... Over the past 30 years, the area subject to melting in Greenland has been increasing at a rate of ~ 17,000 Km2/year. This is equivalent to adding a melt-region the size of Washington State every ten years. Or, in alternative, this means that an area of the size of France melted in 2010 which was not melting in 1979. Au revoir, Paris.
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  2. Muoncounter @53, I just signed on to post the very same image ;) Does it perhaps suggest that the southward extending "limb" of the ice sheet is vulnerable in the coming century or so? If so, any idea how much that would contribute to GSL? The NASA article says 0.6 m by 2100, but does not say where the greatest ice loss will be from.
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  3. Albatross, Sorry, didn't mean to scoop you. I'd have to look at some actual maps, but the EO image sure makes it look like that the southern part could be on the block. Worth checking around to see what other recent images are out.
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  4. @Gordon(50) Several commentators have attributed to me opinions that are not mine. So a couple of clarifications are in order. First, I agree that a sea level rise of a meter in any time period less than 100 years would be terrible. But it is important to treat this figure as an estimate that might or might not be correct, and to contrast it with the current rise rate of one foot per 100 years. Likewise, I do not mean that it will take 40,000 years for the polar ice caps to melt. I do mean that if the melt rate doubles every 5 or 6 years there would still be a lot of ice left in 50 years. I am an optimist about human capabilities. And I don't believe humans can look ahead for more than a few decades. Is that a contradiction? Perhaps. But I find it hard to take seriously projections 50 years or more from now that seem to reject the possibility that humans will take more serious steps to reduce the rate of global warming during the next decade or two or three. I believe we will have time to react at some future date when the data upon which estimates are based is inevitably of better quality. In the interim, I believe it is very important for everyone to compare estimates of future rates with present rates, in order to demonstrate the discrepancy between the two. And numbers like "thousands of gigatons" (or cubic kilometers) are not helpful to general understanding unless they are presented as a ratio.
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  5. Anil Anantheswamy writes in Greenland poised on a knife edge in New Scientist (8 Jan 11, p8), that the ice sheet will reach a tipping point in the early 2040’s, after which nothing mankind does will prevent its eventual collapse. He points out that Greenland’s bedrock dips down, like a soup plate, and that glacier retreat beyond the edge of the dish would result in retreat up to 80 km inland causing huge embayments into the ice sheet. Were this scenario to be realised, how long would it take for the ice sheet to melt? 1,000 years? Adding an average of 0.7m/century to sea level. With loss of Antarctic ice and thermal expansion of seawater, a sea-level rise of ~2m by 2100 seems more realistic than alarmist. Were that to occur, the world as we now know it would cease to exist, particularly for the 70% of global population living on or near the present coast. But fear not. Government intends reducing greenhouse gas emissions by 5% below 2000 levels by 2020 !
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  6. Peter, You cannot have it both ways. Either you think the sea level rise will continue at its present rate or you think it will increase rapidly in the future. In your first paragraph you claim the first and in your second you claim the second. You need to decide what you think the data support. Hand waving optimism is nice, but not very convincing or productive. Current scientific estimates of sea level rise by 2100 range from one to five meters. Do you have any data to suggest these estimates are incorrect? Since we agree that over 1 meter of sea level rise is terrible and current best estimates are for more rise than that, we need to propose what can be done now to change BAU so that these terible things do not occur. Hoping that people at some undefined future date will be smarter than we are, and will have the technology to save themselves is not much of a plan.
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  7. I think Peter's comments point out the weakness of human nature when confronted with a multi-decade problem. (And I mean no disparagement of Peter). As a species we are not good at the 30 year+ type planning. Very few (perhaps more posters here than the world-at-large) begin their retirement savings in their 20s. Sometimes you can get away with it. (My parents started saving for retirement in their 50s and are not retired - not well-off, not even really comfortable, but retired...). The stunning preponderance of evidence is that we CANNOT get away with it in regards to climate change. That when the evidence the deniers (or even well meaning, accepting of reality folks like Peter, looking for the inevitably improved estimates) arrives - the outcomes that are painful and probably not possible to manage will be baked into the pie. We basically need nature to cooperate and throw in some natural-variation-on-the-warm-side or else we can expect more status quo/BAU. If however, fossil fuel prices increase and we have a hot couple of years (El Nino we miss you!) - that might suffice to move people into the take the necessary preventative steps column. This feels like a negative comment, but I am at a loss to justify/explain what people are doing in another way.
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