Related post: Arctic heads for record melt, but do we want to know?

UPDATE 21 August: RECORD SEA-ICE MELT: The Arctic big melt is charging along and a number of data sets today show that 2012 has broken the 2007/2011 record for minimum sea-ice extent / area. These include data sets from Arctic ROOS and Cryosphere Today. This closeup from Neven of the Cryosphere Today data is very clear:

Cryosphere Today sea ice area August 2005-2012

Cryosphere Today data set shows:

• 2012, day 230, 2.87743 million square kilometers
• 2011, day 253, 2.90474 million square kilometers (previous record low)

So it looks like the record has been smashed with another 3 weeks to go in the melt season.  This is almost as extraordinary as the Greenland record melt story below. 


by David Spratt, published 16 August 2012

Greenland melt index (2012 red bar)  Source: Marco Tedesco/Greenland Melting

News today of a dramatic increase in melting of the Greenland ice sheet this northern summer, and the likelihood of a new record low in summer Arctic sea-ice extent, demand a new look at what safe climate action means.
     Today, Marco Tedesco, assistant professor of Earth and atmospheric sciences at The City College of New York, reported that melting over the Greenland ice sheet shattered the seasonal record in the modern era, a full four weeks before the close of the melting season. The melting season in Greenland usually lasts from June – when the first puddles of meltwater appear – to early September, when temperatures cool. This year, cumulative melting by 8 August had already exceeded the record of 2010 (chart above, year 2012 in red). "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," said Professor Tedesco.

Greenland melt in 2012 (Marco Tedesco)

     It is the latest in a rush of dramatic news from the Arctic in recent weeks, where this year’s summer sea-ice melt may well break the record low set in 2007, amid growing expectations of the Arctic becoming sea-ice free in summer within the decade, and perhaps sooner.
     The Arctic, the part of the world where global warming is greatest and where some of the most dramatic impacts are being witnessed, is the canary in climate warming coal mine.
    And the canary is being allowed to die. Arctic summer sea ice cover is in a “death spiral” according to Mark Serreze, director of the US National Snow and Ice Data Centre (NSIDC).
     Only one conclusion can be drawn as the Arctic ecosystem is being rapidly transformed into a landscape that would not have been recognisable a decade or two ago. At just 0.8ºC of global warming, it is already too hot, and climate change has already gone too far if you value a safe climate in which biodiversity and all the world’s marvellous ecosystems are maintained.
     As proposed in A sober assessment of our situation, even the current level of warming for an extended period of time is very risky, yet warming will exceed and be maintained well above 1ºC for the greenhouse gases already in the atmosphere, for all the emissions reduction scenarios now on the political table.
     It is now obvious that as well as reducing greenhouse emissions to zero, drawing down atmospheric carbon on a large-scale is now necessary. And so too is short-term geo-engineering such as incoming radiation management — if it can be done with relative safety — to stop too much warming whilst the other two strategies have time to work to restore a safe climate. We are now living in a world where we have to make the least-worst choices.

2012 IN THE ARCTIC

Headlines this northern summer tell the story:

• Record heat in May rewrote weather records in Greenland, setting the stage for a big summer melt.
• Arctic Ocean floating sea-ice set a record for the largest June sea ice loss in the satellite era. The Arctic lost a record total of about 2.86 million square kilometres of ice. At the end of the month, Arctic sea ice extent was 1.18 million square kilometres below the 1979-to-2000 average.
• In July, NASA released findings showing surface melt of the Greenland ice sheet of more than 97 per cent  over a few days, a rate unprecedented in the era of satellite observation, and pictured in dramatic satellite images. Most previous similar events were clustered around a period 7000 years ago when variations in the sun's axis tilt sent more sunshine to extreme northern latitudes, warming them up. There is no such solar tilt now, but the melt is occurring just the same, according to Mark Serreze.
• In late July, Climate Central reported that that the reflectivity of the Greenland ice sheet, particularly at the high elevations that were involved in the mid-July melt event, had declined to record lows. This indicated that the ice sheet was absorbing more incoming solar energy than normal, potentially leading to 2012 being another record melt year in a long-standing trend of increasingly higher melt seasons. 
• On 15 August, Marco Tedesco's findings of record melting on Greenland were released.
• In early August, a huge, long-lived Arctic ocean storm decimated the sea ice area which was melting out at a record rate, before the high waves and winds shattered the Siberian side of the ice cap.  Sea-ice extent is currently tracking below the previous record low of 2007. 
• New research finds sea ice loss is 50 per cent higher than previously thought. On 10 August, The Guardian reported that data from the first purpose-built satellite launched to study the thickness of the Earth's polar caps – the European Space Agency's CryoSat-2 probe – indicate that 900 cubic kilometres of summer sea ice has disappeared from the Arctic Ocean over the past year, and “in a few years the Arctic ocean could be free of ice in summer, triggering a rush to exploit its fish stocks, oil, minerals and sea routes.”
• The combination of global atmospheric warming, and melting sea ice and changing reflectivity of the Arctic surface, are contributing to the high rate of warming in the Arctic, where temperatures are increasing up to four times faster than the global average.
• The radical decline in sea ice around the Arctic is at least 70% due to human-induced climate change, according to a new study, and may even be up to 95% down to humans – rather higher than scientists had previously thought.

TIPPING POINT

Melting in the Arctic is accelerating, and the region has proved to be more sensitive to global warming than previously thought.
     "Very soon we may experience the iconic moment when, one day in the summer, we look at satellite images and see no sea ice coverage in the Arctic, just open water,” says Dr Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London.
     Runaway loss of Arctic sea ice may now be inevitable and more worrying, and very likely, is the collapse of the giant Greenland ice sheet, according to climate tipping point expert Dr Tim Lenton. He told the Planet Under Pressure conference earlier this year "The (Arctic sea ice) system has passed a tipping point" that could soon make ice-free summers a regular feature across most of the Arctic Ocean, based on a day-by-day assessment of Arctic ice-cover data collected since satellite observation began in 1979.
     In an interview with Bloomberg on 16 August, NASA’s top climate scientist, James Hansen said the increasing sea-ice melt may be a harbinger of greater changes such as the release of methane compounds from frozen soils that could exacerbate warming, and a thaw of the Greenland ice sheet: “Our greatest concern is that loss of Arctic sea ice creates a grave threat of passing two other tipping points -- the potential instability of the Greenland ice sheet and methane hydrates… These latter two tipping points would have consequences that are practically irreversible on time scales of relevance to humanity.”
     And Australia-based scientists say the Arctic region is fast approaching a series of imminent "tipping points" which could trigger a domino effect of large-scale climate change across the entire planet with “major consequences for the future of human kind as climate change progresses." But they observe that “several tipping points, such as the loss of summer sea ice, may be reversible in principle − although hard in practice.”

  A GRAPHIC STORY

Sea ice extent: The following graph shows the extent of summer sea ice in 2012 (blue line) compared to the 1979-200 average (grey line) and the record low of 2007 (dashed green line). The area of ice at the summer minimum in the last five years has been 4.3–4.6 million square kilometres, little more than half of what it was 30 years ago.

Arctic sea ice extent to 13 August 2012. Source: NSIDC

Sea-ice thickness: There is less ice, and it is now much thinner and more fragile. And the proportion of thick, older ice that lasts from one year to the next is shrinking even faster than the area of ice.. Researchers now find that new, first-year ice is less reflective than old ice, for most of the year, anyway. It absorbs more heat from the sun, which means it doesn’t just melt faster: it actually speeds up its own melting.

Sea-ice volume: The new Cryo-Sat2 data suggests that the volume (area multiplied by thickness) has reduced around 70% over the past 30 years. According to CryoSat, in 2004 there was about 13,000 cubic kilometres of summer sea ice in the Arctic. In 2012, there is 7,000 cubic kilometres, a little over half the figure eight years ago. If the current annual loss of around 900 cubic kilometres continues, summer ice coverage could disappear in about a decade in the Arctic. CryoSat “has shown that the Arctic sea cap is not only shrinking in area but is also thinning dramatically."
     This research is very similar to Arctic sea ice volume graph (graph below) as calculated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center. The red line is 2012.

PIOMAS daily ice volume

Predicting the year zero: Using the PIOMAS data (graph below) and depending on what assumption you make about the nature of sea-ice volume decline, “best fit” lines of decline suggest an ice-free Arctic most likely within a decade and perhaps as early as 2015 (red line). Judging by discussions within the cryosphere research community it feels as though more and more scientists now see a summer sea-ice-free Arctic as likely within a decade.

Sea-ice volume trends

Whilst scientists urge caution about the implications of the CryoSat-2 data, the conclusions are nevertheless dramatic. Dr Seymour Laxon, who analysed the data, told the BBC: "We have to be cautious until our data has been properly analysed as part of a climate model, but this does suggest that the Arctic might be ice-free in summer for a day at least by the end of the decade.