Tag: Greenland

Why Arctic sea ice shouldn’t leave anyone cold

In this guest post Neven Acropolis, the man behind the excellent Arctic Sea Ice blog, looks at the reasons why we need to pay attention to the rapid loss of sea ice in the Arctic Ocean.

Arctic sea ice became a recurrent feature on planet Earth around 47 million years ago. Since the start of the current ice age, about 2.5 million years ago, the Arctic Ocean has been completely covered with sea ice. Only during interglacials, like the one we are in now, does some of the sea ice melt during summer, when the top of the planet is oriented a bit more towards the Sun and receives large amounts of sunlight for several summer months. Even then, when winter starts, the ice-free portion of the Arctic Ocean freezes over again with a new layer of sea ice.

Since the dawn of human civilisation, 5000 to 8000 years ago, this annual ebb and flow of melting and freezing Arctic sea ice has been more or less consistent. There were periods when more ice melted during summer, and periods when less melted. However, a radical shift has occurred in recent times.

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Ever since satellites allowed a detailed view of the Arctic and its ice, a pronounced decrease in summer sea ice cover has been observed (with this year setting a new record low). When the IPCC released its Fourth Assessment Report in 2007, it was generally thought that the Arctic could become ice-free somewhere near the end of this century. But changes in the Arctic have progressed at such speed that most experts now think 2030 might see an ice-free Arctic for the first time. Some say it could even happen this decade.

2 albedofeedbackWhat makes this event significant, is the role Arctic sea ice plays as a reflector of solar energy. Ice is white and therefore reflects a large part of incoming sunlight back out to space. But where there is no ice, dark ocean water absorbs most of the sunlight and thus heats up. The less ice there is, the more the water heats up, melting more ice. This feedback has all kinds of consequences for the Arctic region.

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Deep Water

We know that sea level rise is an inevitable consequence of the global warming that our continued burning of fossil fuels is causing. What we don’t know is how much to expect and how soon to expect it. Journalist Daniel Grossman in his Kindle Single Deep Water: As Polar Ice Melts, Scientists Debate How High Our Oceans Will Rise explores the momentous issue by looking at the work of three scientists who study the past history of elevated sea levels to get a better understanding of what is likely ahead for humanity. Grossman writes from a close acquaintance with climate science and his ability to distil the science in readily understandable form for the general reader is outstanding.

Paul Hearty, “talented and cantankerous”, is a geologist who has argued from his studies of inter-glacial periods that if the Earth warms by two degrees the huge glaciers in Greenland and Antarctica could substantially melt in a short space of time. His field work in the Bahamas and Bermuda, which he regards as a relatively stable region geologically, has led him to the conclusion that in the warm interglacial 400,000 years ago (Stage 11) sea level rose by as much as around 19 metres. Paleoclimatologist Maureen Raymo doesn’t share that view but it was Hearty she invited in 2009 to collaborate in field work with her in Western Australia seeking evidence of sea level rise in the Pliocene. Grossman travelled with them as journalist and gives a lively account of the expedition.

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Greenland’s extraordinary summer #3: new record melt year, and summer’s not over yet

Greenland’s amazing summer continues, with news today that the ice sheet has already set a new record for surface melting — with four weeks of the melt season still to run. The ice sheet surpassed the previous record year, 2010, on August 8th. Marco Tedesco of the City College of New York said:

“With more yet to come in August, this year’s overall melting will fall way above the old records. That’s a goliath year – the greatest melt since satellite recording began in 1979.”

Tedesco and his team calculate the duration and extent of melt over the ice sheet, using satellite data to develop a ‘cumulative melting index’. The index is defined as the number of days when melting occurs multiplied by the total area subject to melting, and is a measure of how much melting has occurred in a season that normally runs from June to September. As the chart below demonstrates, by August 8th the melt was already well ahead of 2010.

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So far this year Greenland has experienced extreme melt in virtually every corner of the ice sheet, and especially at high altitudes. When summer’s over, and the research teams ponder the data they’ve gathered on the ice, it seems pretty clear that there are going to be some interesting figures to consider, with consequences for everyone with beachfront property… Follow Tedesco’s work, and that of other teams working on Greenland on his Greenland Melting site.

Greenland’s extraordinary summer #2: still melting

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Greenland’s extraordinary summer is far from over. The ice island that broke off the Petermann glacier tongue last month — now dubbed PII-2012 — is edging its way out into the Nares Strait between Greenland and Ellesmere Island, as this satellite image, snipped from NASA’s fabulous daily Arctic Mosaic shows. For updates on events in Nares Strait, check out Dr Andreas Muenchow’s Icy Seas blog — he’s up there at the moment. Elsewhere on the great ice sheet, melting continues apace. Jason Box reports that ice sheet albedo has dipped again into record levels for the time of year, and there are reports of further extensive surface melting at the end of July. Box also reports that a recent update of the Greenland temperature record shows that current temperatures are unprecedented in at least the last 172 years. There’s also excellent coverage of the summer at Greenland melting.

Meanwhile, and rather unsurprisingly, New Zealand’s little band of climate deniers are insisting that there’s nothing special going on up North. And, equally unsurprisingly, they’re totally wrong.

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Favourite worst nightmare

The summer melt season in the Arctic is approaching its annual climax — the sea ice minimum, due in September — and the picture is beginning to look grim. Sea ice extent and area are tracking 2007’s record-setting melt, ice volume is at record lows for the time of year, and the ice is looking very fragmented, making it vulnerable to rapid melting events. To make matters worse, a large storm is brewing over the Arctic ocean, and is likely to create a surge of ice loss. 2012 could be heading towards breaking 2007’s record minimum, and that’s bad news for the entire northern hemisphere.

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