|Arctic sea-ice extent, 4/22/2015, Red line is 2015|
source: NORSEX SSM/I
The graph at the right shows a close-up of sea-ice extent data from NORSEX for the past few years, with the red line indicating extent for 2015 (see link). What caught my attention is the relative flat-ness of the red line, compared to most of the earlier years. The graph shows ice extent in millions of square kilometers on the vertical axis. The horizontal axis shows time in approximately 10 day increments (three increments for each month), with January 1 at the far left.
Is this normal, or unprecedented? Careful inspection of the graph shows that the light green line, representing the data for 2011, also had a similar flat trend over the same period. Therefore, the flat trend for this year has a precedent.
One can also speculate on the reasons for the ice not melting at the "normal" rate, where "normal" is provided by the blue dotted line. The blue dots represent the monthly average of the period 1979 - 2006. The slope of the blue dotted line from the maximum (roughly March 10th) to April 22 is (very roughly estimated) 15 million to 14 million, or a decrease of 1 million square kilometers. Yet this year, only (roughly) one-third that amount of ice melted. Could the reason be that CO2 in the atmosphere is not getting the job done? Are there clouds over the Arctic this year, preventing solar heat from hitting the ice? Are the ocean currents that enter the Arctic colder than usual this year? Is the black carbon soot that normally falls on the ice absent this year? Perhaps the Arctic winds are not blowing the ice floes to the south, where they meet warmer waters and melt.
I don't know the answer or answers. What I do know is that the ice is not melting this year, at least not at the historic rate.
Roger E. Sowell, Esq.
Marina del Rey, California
Copyright (c) 2015 by Roger Sowell