Tag: albedo

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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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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Greenland’s extraordinary summer: melting records and ice island setting sail

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July has been an amazing month in Greenland. The Petermann Glacier has given birth to another huge ice island — taking its terminus further back up its fjord than at any time in the last 100 years (at least), record high temperatures have been recorded at the summit of the ice sheet at 3,200 meters, initiating surface melt over the whole vast sheet, ice sheet albedo has plummeted, and the Jakobshavn Isbrae’s calving front has retreated into the ice sheet.

The best coverage of the Petermann event, as on most matters to do with the Arctic summer and sea ice melting season is to be found at Neven’s Arctic Sea Ice blog. It’s well worth reading the comments under the Petermann post there, to get a really informative picture of what’s being going on. Here’s a description by Dr Andreas Muenchow ((Andreas provides great coverage of the Petermann glacier at his blog — perhaps unsurprisingly, as he’s on his way up there to recover instrumentation soon.)) of what the calving would have been like:

I described the Petermann calving to some media folks as a gentle and very quiet affair similar to a rubber duckie pushed out to sea from the deck of a flat pool.

Some duckie, some pool…

Illulisatanimated2012203Further south, the the “root” of the Jakobshavn Isbrae has enlarged significantly, with the calving front of Greenland’s most productive glacier retreating further into the ice sheet. The “blink” image I’ve cobbled together (left) shows day 203 of this year compared with day 202 of last year ((Source: 2012, 2011.)). The difference is large and very obvious. Greenland specialist Dr Jason Box was flying out of Ilulisat shortly after the retreat earlier this month, and snapped the photo below out of the window of his plane. As he commented on Facebook, it looks like the glacier has divided into two streams.

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Up at the summit of the Greenland ice sheet at 3,200 metres, a new high temperature record of 3.6ºC was set on July 16, hard on the heels of four days in row of temperatures above freezing, from July 11 to 14. Considering that temperatures above zero had only been recorded four times in the preceding 12 years, this amounted a remarkable heatwave, and triggered an astonishing melt record.

Greenlandmelt2012

This NASA graphic shows how the melting surface, shown in shades of red, spread over the whole surface of the ice sheet from July 8 to July 12. This amounts to “the largest extent of surface melting observed in three decades of satellite observations”, according to NASA. The last such melting event occurred in 1889, and ice cores show that they occur every 150 to 250 years. However, given the steady increase in melt area over the last decade, and the precipitous drop in ice sheet albedo (see below), especially at high altitudes, it may not be 150 years before such a melt happens again.

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The last time I looked at this extraordinary summer in Greenland, it was to report Jason Box‘s view that “it is reasonable to expect 100% melt area over the ice sheet within another similar decade of warming”. It took two weeks to come true. Forgive me if I find that alarming.

Wake Up, Freak Out – then Get a Grip

Excellent animation by Leo Murray explaining climate system feedbacks and the potential for us to pass “tipping points” that could make our efforts to reduce emissions completely redundant. More information (including script and references) at wakeupfreakout.org. Hat-tip to Peter “Crock of the Week” Sinclair for finding it…