Analysis suggests Arctic sea ice is more stable than thought
Yesterday, I pointed out that despite predictions of an “ice-free summer” in the Arctic by now, Arctic sea ice continues to defy such predictions and ended the 2018 melt season higher that the lowest years of 2012 and 2007:
Ron Clutz writes and provides a graph that suggests the Arctic sea ice has reached a new, but lower, equilibrium point since 2007:
People are overthinking and over-analyzing Arctic Ice extents, and getting wrapped around the axle (or should I say axis). So let’s keep it simple and we can all readily understand what is happening up North.
I will use the ever popular NOAA dataset derived from satellite passive microwave sensors. It sometimes understates the ice extents, but everyone refers to it and it is complete from 1979 to 2017. Here’s what NOAA reports (in M km2):
If I were adding this to the Ice House of Mirrors, the name would be The X-Ray Ice Mirror, because it looks into the structure of the time series. For even more clarity and simplicity, here is the table:
NOAA NH Annual Average Ice Extents (in M km2). Sea Ice Index v2.1 (here)
|Year||Average||Change||Rate of Change|
|1994||12.011||-0.317||0.021 per year|
|2007||10.474||-1.537||0.118 per year|
|2017||10.393||-0.081||0.008 per year|
The satellites involve rocket science, but this does not. There was a small loss of ice extent over the first 15 years, then a dramatic downturn for 13 years, 6 times the rate as before. That was followed by the current plateau with virtually no further loss of ice extent. All the fuss is over that middle period, and we know what caused it. A lot of multi-year ice was flushed out through the Fram Strait, leaving behind more easily melted younger ice. The effects from that natural occurrence bottomed out in 2007.
Kwok et al say this about the Variability of Fram Strait ice flux:
The average winter area flux over the 18-year record (1978–1996) is 670,000 km2, ;7% of the area of the Arctic Ocean. The winter area flux ranges from a minimum of 450,000 km2 in 1984 to a maximum of 906,000 km2 in 1995. . .The average winter volume flux over the winters of October 1990 through May 1995 is 1745 km3 ranging from a low of 1375 km3 in the 1990 flux to a high of 2791 km3 in 1994.
Some complain it is too soon to say Arctic Ice is recovering, or that 2007 is a true change point. The same people were quick to jump on a declining period after 1994 as evidence of a “Death Spiral.”
via Watts Up With That? https://ift.tt/1Viafi3