2011 has seen new record lows established for Arctic average sea ice extent and area; sea ice volume; and for global sea ice area.

Neven at Arctic Sea Ice Blog reports that the 12 month rolling average for Arctic sea ice extent set a new record in October 2011 at 10.66 million km². The previous record of 10.67 million km² had been set in October 2007.

The record for Arctic sea ice area has also been broken. The October 2007 was again the previous record, standing at 8.39 million km². Annual average Sea Ice Area dropped to 8.34 million km² for the 12-month period ending in October 2011.

Sea ice volumes have been decreasing far more quickly. The previous record value from PIOMAS was 15,075 km³, set in the 12-month period ending in January 2008, a record that held for just 29 months. The 12-month period ending in September 2011 set a new record, averaging 13,140 km³.

Global sea ice area (Arctic and Antarctic combined, as calculated at Cryosphere Today) has also reached its lowest maximum on record, as seen in this graph posted here.

It’s hard to see the new record in the graph above, but Neven posts this chart showing the numbers.

Earth’s cryosphere continues to wither under the assault from global warming.

A new study published in Nature Geoscience by Ian Joughin and Richard B. Alley titled Stability of the West Antarctic ice sheet in a warming world reports recent observations by satellite show substantial mass loss from the West Antarctic ice sheet (WAIS).

Losses range from 100 to 200 gigatonnes per year, the equivalent to 0.28 to 0.56 mm per year sea-level rise – and the rate is increasing.

This excerpt is from the abstract:

Ice sheets are expected to shrink in size as the world warms, which in turn will raise sea level. The West Antarctic ice sheet is of particular concern, because it was probably much smaller at times during the past million years when temperatures were comparable to levels that might be reached or exceeded within the next few centuries. Much of the grounded ice in West Antarctica lies on a bed that deepens inland and extends well below sea level. Oceanic and atmospheric warming threaten to reduce or eliminate the floating ice shelves that buttress the ice sheet at present. Loss of the ice shelves would accelerate the flow of non-floating ice near the coast. Because of the slope of the sea bed, the consequent thinning could ultimately float much of the ice sheet’s interior. In this scenario, global sea level would rise by more than three metres, at an unknown rate.

The study’s authors suggest loss of the large ice shelves by atmospheric or oceanic forcing would probably lead to collapse of the bulk of the marine ice sheet. Temperature predications for 2100 approach the thresholds of ice-shelf viability in many simulations.

With CO2 emissions increasing by a record amount in 2010, temperatures by the end of the century are likely to be at the top end of or even exceed IPCC predictions. Meeting the 2° target the IPCC warns is necessary to avert dangerous climate change depends on limiting atmospheric CO2 to no more than 450 ppm. We are a little below 400 parts per million now – and heading higher. Recent research has found that the WAIS collapsed and rebuilt multiple times matching the cycle of Northern Hemisphere’s pattern of glaciation and glacier retreat – collapsing much more frequently when atmospheric CO2 hit 400ppm.

Sea level rise is now going up about 3.5 centimeters per decade. A collapse of the marine ice sheet in West Antarctica would raise sea levels by more than three meters over the course of several centuries or less – in the past, sea levels have risen at a speed of up to one meter per 20 years.

It’s bad enough that the Greenland ice sheet is melting: Greenland setting a new melt record in 2010, and Greenland melting in 2011 well above average with near-record mass loss. Now we may be witnessing the start of the destabilization of the WAIS.

Scientists have produced the first map of ice motion over the entire continent of Antarctica. From the air, the Antarctic continent appears a featureless, static icy remnant of the past. However, the new satellite-based pole-to-coast map reveals sinuous, river-like streams of ice and their speed of discharge from central Antarctica into the ocean.

The map is published online by Science magazine (subscription only). The visualization reveals the extent of the sinuous, river-like streams of ice and the speed of discharge from central Antarctica into the ocean. It’s available from BBC News (better yet, from the European Space Agency (ESA), without the commercial). The new findings should shed new light on the contribution of Antarctic ice sheets  to sea-level rise.

The map incorporates billions of radar data points collected between 1996 and 2009 by satellites belonging to Europe, Canada and Japan; and includes data from East Antarctica which has never before been available. While the broad picture of how the ice drains from the center of Antarctica to the edges has been reasonably well understood, the map reveals a number of previously unrecognized features, including a ridge that splits the 14 million square km landmass from east to west.

Ice velocities on the new map range from just few centimeters per year near places where the ice divides into different paths, to kilometers per year on fast-moving glaciers and the ice shelves that float out from the edges of the continent. Ice flow is fastest at the Pine Island and Thwaites glaciers in West Antarctica. Recent survey work has revealed that Pine Island is thinning rapidly; its surface has been dropping by more than 15m per year.

The ESA confirms both Arctic sea routes are once again open at the same time, for the fourth consecutive year.

The long-sought Northwest Passage opened for the first time in 2007. Now, it’s routine.

In 2008 satellites saw that the Northwest Passage and the Northern Sea Route were open simultaneously for the first time since satellite measurements began in the 1970s – and now it has happened again.

While the Northern Sea Route above Russia (also known as the Northeast Passage) has been open to shipping traffic since mid-August, recent satellite data show that the most direct course in the Northwest Passage now appears to be navigable as well.Located in the Canadian Arctic Archipelago, the Northwest Passage can be a short cut for shipping between Europe and Asia – but with the opening of the sea route comes the potential for both sovereignty claims and marine species migration across the Arctic Ocean.

In 2007, Arctic sea ice hit a record low since satellite measurements began nearly 30 years before. That same year, the historically impassable Northwest Passage opened for the first time.

Unusual weather contributed to 2007’s record ice loss: skies opened over the central Arctic Ocean and wind patterns pushed warm air into the region, promoting a strong melt.

Weather patterns have been different this year, but the early opening of the passages indicates that we could be about to hit a new record low in ice cover.

Leif Toudal Pedersen, senior scientist at the Danish Meteorological Institute, explains:

The minimum ice extent is still three to four weeks away, and a lot depends on the weather conditions over the Arctic during those weeks. Whether we reach an absolute minimum or not, this year again confirms that we are in a new regime with substantially less summer ice than before. The last five summers are the five minimum ice extent summers on record.

It’s now undeniable that humans will be living with a new and different Arctic – and Antarctic, too.

A new NASA-funded study finds that the Greenland and Antarctic ice sheets are losing mass at an ever-accelerating pace.

Total ice sheet mass balance between 1992 and 2009, as measured for Greenland (top), Antarctica (middle) and the cumulative sum of both ice sheets (bottom), in gigatonnes per year. A straight line in these figures (with negative mass balance) would be a constant loss of ice, the slope indicates that the loss is increasing over the last twenty years.

The team found that for each year over the 18-year study, the Greenland ice sheet lost mass faster than it did the year before, by an average of 21.9 gigatonnes a year. In Antarctica, the year-over-year speedup in ice mass lost averaged 14.5 gigatonnes. The two ice sheets lost a combined average of 36.3 gigatonnes more than they did the year before. Lead author Eric Rignot, jointly of NASA’s Jet Propulsion Laboratory, Pasadena, CA and the University of California, Irvine said this means sea levels will rise more than previously thought:

What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations Intergovernmental Panel on Climate Change in 2007.

The authors conclude that if this trend continues, ice sheets will be the dominant contributor to sea level rise in the 21st century.

Due to a lack of basis in published literature, the IPCC’s models did not consider ice sheet flow. The IPCC’s 4th Assessment Report estimated that sea level rise would be 18 to 38 cm (7 to 15 inches) in a low scenario and 26 to 59 cm (10 to 23 inches) in a high scenario.

Study results are published this month in Geophysical Research Letters.

New analyses of the heat content of the waters off Western Antarctic Peninsula are now showing a clear and exponential increase in warming waters – undermining the sea ice, raising air temperatures, and melting glaciers.

Says physical oceanographer Doug Martinson of the Lamont-Doherty Earth Observatory, who has been collecting ocean water heat content data for more than 18 years at Palmer Island, on the western side of the Antarctic Peninsula:

In the area I work there is the highest increase in temperatures of anywhere on Earth. Eighty-seven percent of the alpine glaciers are in retreat. Some of the Adele penguin colonies have already gone extinct.

The extraordinary warming of the Antarctic Peninsula shows up clearly on new global warming maps released by NASA:

The map shows temperature anomalies for 2000-2009 and 1970-1979 relative to a 1951-1980 baseline. The average global temperature has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880. About two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade.

What the rising water heat means, according to Martinson, is that even if humanity got organized and stopped emitting greenhouse gases tomorrow, there is already too much heat in the oceans to stop a lot of impacts – like the melting of a huge amount of Antarctic ice.

A study published in the journal Global Change Biology reports the discovery of very similar colonies of bryozoans – animals that anchor themselves to the seabed – in both the Ross and Weddell Seas.

The bryozoans, sometimes called moss animals, are often microscopic as individuals but form colonies that can look like corals or some seaweeds. Those found were unlike others around the current coast of Antarctica.

So,what’s the big deal?

Bryozoans are largely static and their larvae, dispersed by currents, are short-lived and quickly sink. How is it possible that two virtually identical populations came to exist 2400 kilometers apart, separated by the 2 kilometre thick West Antarctic ice sheet?

An article at ABC News in Science quotes lead author David Barnes:

The most likely explanation of such similarity is that this ice sheet is much less stable than previously thought and has collapsed at some point in the recent past. And if the West Antarctic ice shelf has been lost in recent times we have to re-think the possibility of loss in future with climate change.

If the ice were gone a passage would become open through which currents could carry the larvae between the two seas.

Melting of the West Antarctica ice cap would raise world sea levels by between 3.5 and 5 meters. In a brief warm period about 125,000 years ago, world sea levels were about five meters higher than today and temperatures probably at least 4°C warmer.

A good friend recently asked me why I give so much attention to news about Arctic sea ice extent at this blog, saying he just glosses over posts on this subject.

Here’s the reason: the area of sea ice cover is an important, amplifying climate feedback. Loss of sea ice is a cause of concern because as the area of ice decreases, increased absorption of sunlight by the darker ocean causes more sea ice melting. As this graph from Makiko Sato & James Hansen’s new blog shows, Arctic sea ice extent has been declining steadily . . .

. . . as has sea ice volume. What ice remains is getting thinner.

It’s not just sea ice that is melting. Ice sheets are shrinking too, both in Greenland and in Antarctica.

And the ice loss over the last few years has been at a time of minimum solar irradiance. Solar irradiance is now once again on the upswing.

It seems likely that September Arctic sea ice may be all but gone within a few decades – or perhaps even sooner. What does less Arctic sea ice mean for Earth’s weather patterns?

NASA is predicting loss of summer sea ice will mean more severe winter storms in the northern hemisphere – a prediction which is already being borne out.

Following Arctic sea ice extent is fascinating because it shows that global warming is not something to worry about in the future. Global warming is here and now, and is already affecting us in our daily lives. What’s worrisome is that the impacts will only get more severe. By the time the impacts are bad enough to get our attention, it will be too late – the damage will already have been done. Under the best-case scenario it will take Earth a thousand years or more to recover. Under the worst-case scenario, Earth will flip into a different, stable climate regime which won’t be hospitable to human existence.

In Antarctica, a robot submarine sent beneath the Pine Island glacier’s floating ice sheet has shown that the glacier has become unpinned from an undersea ridge and that warm water is now circulating under the ice, causing the glacier to melt even faster in an accelerating feedback loop.

The study, Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat, is published in Nature Geoscience.

The 400 meter- high ridge has previously been anchoring the glacier and preventing warm seawater from reaching the ice, melting it from underneath.  A modeling study published in January suggested that once the glacier retreated behind the ridge, the glacier would not be able to recover.

Pine Island glacier is one of a handful in West Antarctica which together are estimated to be responsible for about 10% of global sea-level rise.

At the other end of the world, scientists are predicting that September 2010 will see yet another “critical minimum” for Arctic sea ice.

One forecast, contained in the September Sea Ice Outlook: June Report, was developed by the team from Klima Campus of the University of Hamburg. It estimates a September minimum of 4.7 million square kilometers. Another estimate produced by AWI researchers is a bit higher – 5.2 million km². Neither of the two research groups anticipates that the record minimum of 4.3 million km² in 2007 will be reached. But scientists caution that the decisive factors for the situation in late summer, such as the ice thickness in the central Arctic and further development of the weather in summer, are not yet known.

What is known is that Arctic sea ice volume is falling off a cliff.

Continuously updated Arctic Sea Ice Volume Anomaly from PIOMAS. Daily Sea Ice volume anomalies for each day are computed relative to the 1979 to 2009 average for that day. The trend for the 1979- present period is shown in blue. Shaded areas show one and two standard deviations from the trend. Click on image for a larger version of the figure

Evidence from an Antarctic geological research drilling program known as ANDRILL suggests that the vast East Antarctic Ice Sheet, which holds at least four-fifths of the continent’s ice, is more susceptible to melting than previously thought and that an abrupt shrinkage of its ice sheets at some greenhouse gas threshold is possible, perhaps beginning within in this century.

The southern McMurdo Sound core yielded clear evidence of some 74 cycles of ice sheet buildup and retreat during a 6-million-year stretch starting in the Miocene Epoch some 20 million years ago. According to geologist Robert DeConto of the University of Massachusetts, Amherst, the policy implications are grim, as many population centers worldwide are within a few meters of sea level.

Our models may be dramatically underestimating how much worse it’s going to get. We’re seeing ice retreat faster and more dramatically than any model predicts.

The answer to the puzzling disparity between model predictions and the core data could lie in an erroneous assumption about Antarctica itself. Some parts of the land underlying the East ice sheet might be much lower than currently believed. As warming oceans strip away the surrounding ice shelves, significant chunks of the ice sheet could slide into the ocean.

A prior core, extracted from the McMurdo Ice Shelf between October 2006 and January 2007, indicated that the West Antarctic Ice Sheet has frequently advanced and retreated.

An article in Pysorg.com reports that a huge iceberg has broken off of Antarctica:

An iceberg the size of Luxembourg knocked loose from the Antarctic continent earlier this month could disrupt the ocean currents driving weather patterns around the globe, researchers said Thursday.

Another iceberg known as B9B, which had been jammed against the Antarctic continent for more than 20 years, began to drift and smashed into the Metz tongue.

I found this satellite picture of the event at the European Space Agency website:

The 2550 square-kilometer (985 square-mile) block broke off on February 12 or 13 from the Mertz Glacier Tongue, a 160-kilometer spit of floating ice protruding into the Southern Ocean from East Antarctica due south of Melbourne. B9B is a remnant of a 2,000-square-mile iceberg that calved in 1987, making it one of the largest icebergs ever recorded in Antarctica.

The resulting new iceberg, along with B9B, have since drifted into an adjoining area called a ploynya – an area that produce dense water, super cold and rich in salt, that sinks to the bottom of the sea and drives the conveyor-belt like circulation around the globe. The Metz Glacier Polynya is particularly strong and accounts for 20 percent of the “bottom water” in the world.

Benoit Legresy, a French glaciologist who works at the Laboratory for Geophysics and Oceanographic Space Research in Toulouse and who has been monitoring the Metz glacier, explains how the icebergs could possibly disrupt ocean circulation patterns:

[I]f they stay in this area – which is likely – they could block the production of this dense water, essentially putting a lid on the polynya.