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 km^2, 7% of the area of the Arctic Ocean. The winter area flux ranges from a minimum of 450,000 km^2 in 1984 to a maximum of 906,000 km^2 in 1995. . . The average winter volume flux over the winters of October 1990 through May 1995 is 1745 km^3 ranging from a low of 1375 km^3 in the 1990 flux to a high of 2791 km^3 in 1994.