As you can see from today’s NSIDC graph (there’s always at least a one-day lag in the graph) the 2008-2009 refreeze rate has dropped to and continued at the same level as the 2007-2008 rate for a couple of weeks now.This is well below the 1979-2000 average and is indicative of an overall warming trend.
If the trend line continues as is or drops below the 2007-2008 line we are likely to seem a very heavy melt season in spring-summer 2009. It is important to remember that the new ice is thin, being first year ice and will be very susceptible to melting. See this earlier post for more detail.
Below is the latest NSIDC image of sea-ice extent. The orange lines indicate average sea-ice extent for this day for the period 1979-2000. And remember these are measurements of sea ice extent, not volume. In fact this last year set a record for minimum sea-ice volume.
Last year (2008) was also interesting because Arctic sea-surface temperature were up to 7 degrees warmer than the average.
Image from National Snow and Ice Data Center
Most of the focus in the press is on Arctic Sea Ice, which is as it should be given it’s startlingly accelerated melt rate, but something interesting is going on in Antarctica as well. While Arctic sea ice has been melting, Antarctic sea ice has been increasing, albeit at a much slower rate than the Arctic decrease. Although, at first blow, this might look like supporting evidence for the denialist/delayer position it turns out that this increase is not unexpected and is even predicted by some of the climate models. The fact is that it is further disturbing evidence of the reality of Climaticide.
Sea ice climatologies: Arctic and Antarctic sea ice concentration climatology from 1979-2000, at the approximate seasonal maximum and minimum levels based on passive microwave satellite data. Image provided by National Snow and Ice Data Center, University of Colorado, Boulder.
It’s important to keep in mind that the Arctic and Antarctic are geographically dissimilar, so it’s not too surprising that their sea-ice situations would vary. The Arctic consists of a largely frozen ocean surrounded by such land masses as Canada, Alaska, and Russia. Its southern cousin, meanwhile, is almost the exact opposite—a land mass surrounded by ocean on all sides.
Because it’s semi-landlocked, and thus less buffeted by ocean currents and winds, the Arctic tends to have more moderate seasonal swings in sea ice coverage. While Arctic sea ice can persist for many years, much of Antarctica’s sea ice tends to form and disappear quickly—and somewhat unpredictably.
Satellite monitoring of Antarctica’s sea ice began in 1972, and for the first six years there was an alarming reduction in coverage every year. But to the bemusement of scientists, the trend began to reverse itself in 1978. Since then, the surface area covered by the continent’s sea ice has expanded by an average of 0.5 percent annually; however, it’s a matter of debate whether sea ice covers as much territory today as it once did in the early 1970s.
No one’s entirely sure what’s causing the expansion of sea ice in Antarctica, but the likeliest explanation is a disturbing one. According to a 2005 NASA-funded study, warmer temperatures have caused greater snowfall around the continent’s edges, where the open oceans provide plenty of raw material for precipitation. (Warmer air absorbs moisture more readily.) The weight of that excess snow pushes sheets of sea ice down into the water, causing more water to freeze.
The incremental expansion of Antarctica’s sea ice has coincided with some more troubling changes. Four of the continent’s largest glaciers (whose fates are largely unrelated to that of sea ice) are retreating rapidly, and researchers blame increases in ocean temperature. The diminishment of such massive glaciers means that, despite the slow creep forward of the continent’s sea ice, the total mass of all Antarctic ice—which includes inland ice—has experienced a marked decrease. And a continuation of that trend could lead to significant rises in global sea levels. Furthermore, snow is melting much farther inland than ever, as well as high up in the Transantarctic Mountains. [emphasis–JR]
As mentioned above, denialist/delayers who are specialists in cherry-picking the data and ignoring the complex cause-effect relationships between the earth’s atmosphere, hydrosphere, land areas and biota, try to use the increase in Antarctic sea ice as evidence that the world is cooling. They ignore the logical explanation posted above for Antarctic sea-ice increase while also ignoring the sharp rise in Arctic temperatures, the melting away of ice shelves in both the Arctic and Antarctic (the Wilkins ice shelf lost a big chunk in the Arctic Winter(!) and is now expected to collapse completely at any time)
By the way, it is interesting to note that the Antarctic sea-ice melt for this year is below last year’s trend line bringing it closer to the 1979-2000 average.
The apparent contradiction (apparent only if you are ignorant of the science) between Arctic and Antarctic sea ice behavior is used by denialists/delayers (DD’s) to create doubt about This supposed cooling [it isn’t happening], according to the denialists/delayers is the result of a decrease in solar radiation (since human beings have no significant influence on the planet’s climate).
DD’s frequently misinterpret scientific articles, whether out of ignorance or malice is not always clear, in order to support their anti-global-warming positions. This was the case recently with a peer-reviewed paper by Dr. Anja Eichler of the Paul Scherrer Institute and colleagues. The DD’s claimed that Dr. Eichler’s paper supported their claim that solar radiation was the chief forcing for climate change. Joe Romm of Climate Progress was so outraged by the DD’s claims that he conducted an email interview with Dr. Eichler to clarify the matter.
ROMM: Am I correct that your study was NOT saying human-caused emissions were NOT the major factor driving the temperature record in the past century?
EICHLER: Yes, this is correct. We did a strong differentiation between preindustrial (1250-1850) time and the last 150 years. In the preindustrial time we found a strong correlation between the solar activity proxy and our temperature, suggesting solar forcing as a main force for temperature change in this time. However, the correlation between the solar activity proxy and Altai temperature is NOT significant anymore for the last 150 years. In this time the increase in the CO2 concentrations is significantly correlated with our temperature.
ROMM: Am I correct that your final sentence [in the paper] was merely saying that your results suggest the Sun was responsible for under 50% of the warming since 1900, but you were NOT saying your results shows that the Sun was in fact responsible for half the warming.
EICHLER: This is also absolutely correct.
She added that “uncertainties of our data” do not allow it to be used to give an exact percentage for how much solar activity was responsible for the warming in the past century. Other recent studies have concluded that the Sun’s contribution to recent warming is “negligible.”[emphasis–Joe Romm]
So, in summary, everything is as expected: Arctic sea ice is shrinking, Antarctic sea ice is growing and denialist/delayers are continuing to distort and misinterpret the science.
Crossposted at Daily Kos