Tag: Arctic sea ice

Thin ice #2

New analysis of Icesat data by a NASA team headed by Ron Kwok shows that from 2004 to 2008 Arctic winter sea ice “thinned dramatically”. Icesat measures the “freeboard” of the sea ice, the amount above water level. The graph below shows the extent of the decline, which is most marked in multi-year ice (ice that survives more than one summer).

Icethickness09.jpg

[Click image for bigger version]

In 2003, 62 percent of the Arctic’s total ice volume was stored in multi-year ice, with 38 percent stored in first-year seasonal ice. By 2008, 68 percent of the total ice volume was first-year ice, with 32 percent multi-year.

The information on ice thickness is critical to understanding what’s going on in the Arctic, as Kwok notes:

“Ice volume allows us to calculate annual ice production and gives us an inventory of the freshwater and total ice mass stored in Arctic sea ice,” said Kwok. “Even in years when the overall extent of sea ice remains stable or grows slightly, the thickness and volume of the ice cover is continuing to decline, making the ice more vulnerable to continued shrinkage. Our data will help scientists better understand how fast the volume of Arctic ice is decreasing and how soon we might see a nearly ice-free Arctic in the summer.”

NASA also provide some very nice visualisations of the data: animations of the changes in autumn and winter ice thickness as well as still images. Well worth a look. For more about NASA’s work on thickness, check this earlier post.

Also well worth checking out: The Standard posts a report a lecture about Andrill and the West Antarctic ice sheet by Prof Tim Naish. Earlier in the week, the Herald also reported on a lecture by Prof Peter Barrett that covered similar ground. I’m hoping to persuade the good professors to provide more detail here sometime soon…

The thin ice of a new day

arctic.seaice.color090705.jpgThe National Snow and Ice Data Centre (NSIDC) has just published its July sea ice news update on the state of the Arctic and the progress of the melt season. Under the heading Melt season in high gear, it gives an overview of June events, and the conditions at the start of the period of most rapid melt. Most interesting is their comment that weather patterns over the month were similar to those of 2007, when the record minimum was set:

This contrast between high and low pressure is broadly similar to the atmospheric circulation pattern that set up in 2007. In 2007, that pattern contributed to a significantly accelerated decline in ice extent during July, and a record minimum low in September. Will the same acceleration in ice melt occur this year? If so, a new record low minimum extent becomes more likely. So far, an acceleration has not been observed.

On the other hand, a peek at the IJIS graph shows that 2009 (red) has dipped below last year at the same time, and Cryosphere Today is showing large areas of ice break up (click on the thumbnail above for a larger version). CT’s metric (area, not extent) is also showing a steep decline. No sign of the fat lady yet…

Gone too soon

SIOJune2009iceages.jpg The June Sea Ice Outlook forecasts for the Arctic sea ice September minimum extent have been released today by SEARCH. Most groups are picking a minimum close to last year’s 4.7m km2, but the melt season is starting with an unusually small amount of multi-year ice. The report suggests that there is “a small but important probability of a major sea ice loss event this year, given that the ice is thinner and younger than previous years, combined with a possibility of atmospheric conditions that cause significant ice retreat.” The full range of forecasts is shown in this chart:

SIO_JuneReport2009.gif

The range of individual outlook values is from 4.2 to 5.0 million square kilometers. All estimates are well below the 1979–2007 September climatological mean value of 6.7 million square kilometers. Half of the responses are in the range of 4.9–5.0 million square kilometers; the remaining estimates are in the range of 4.2–4.7 (Figure 1, above). The uncertainty / error values, from those groups that provided them, are close to 0.5 million square kilometers, thus many of the values overlap.

Interestingly, the forecasts showing the lowest minima are based on sea ice modelling driven by atmospheric forcings and initialised with current sea ice conditions. The projection by Jinlun Zhang (next to lowest in the chart) suggests that even with conditions like last year — that is, without the Transpolar Express of warm southerlies that set up in 2007 — the 2007 record could fall. On the other hand, a Russian scientist suggest thats Pacific sea surface temps could be priming a cooler pattern than last year.

The full report [PDF] is a very interesting read for all ice watchers (and gamblers). On this guide to the form, it looks as though I’ll lose my bets – but the weather over the next two months will be the deciding factor. Do I feel lucky…?

[Michael Jackson RIP]

A long way from Home

homer.jpgFilm review corner: Dr Ron Smith, a senior lecturer at the University of Waikato and a regular contributor to Muriel Newman’s crank echochamber went to see Yann Arthus-Bertrand’s film Home earlier this month (previewed here), and was moved to provide Muriel with a review. As crank effluvia go, it’s a classic…

Continue reading “A long way from Home”

Copenhagen 2: dangers ahead

cop_logo_1_r_editedThe second section of the Copenhagen synthesis report, Social and Environmental Disruption, discusses the dangers of climate change relating to society and the environment, noting that scientific research provides a wealth of relevant information which is not receiving the attention one might expect.    

Considerable support has developed for containing the rise in global temperature to a maximum of 2 degrees centigrade above pre-industrial levels, often referred to as the 2 degrees guardrail. The report however indicates that even at temperature rises less than 2 degrees impacts can be significant, though some societies could cope through pro-active adaptation strategies.  Beyond 2 degrees the possibilities for adaptation of societies and ecosystems rapidly decline, with an increasing risk of social disruption through health impacts, water shortages and food insecurity.

Continue reading “Copenhagen 2: dangers ahead”