It looks likely that 2015 annual average ice extent will be lower than 2014, and some will claim this proves global warming is alive and well. But analysis of the details tells a different story.
Firstly, there were many factors working against Arctic ice this year:
- Lower March maximum;
- Warm Blob in the Pacific melting out both Okhotsk and Bering Sea earlier than usual;
- Negative AO most of the summer, ensuring higher insolation and melting;
- Strong storm in August when ice edges are most fragile.
Hidden in the measurements is perhaps the most important factor affecting Arctic ice extent year over year: Variability in Barents Sea ice due to ingress of warm water from the North Atlantic.
Back in April 2015, Dr. Arnd Bernaerts pointed out that this year’s ice was lagging mainly because of Barents and Okhotsk melting out early. (Here). And he also implicated various offshore marine operations: shipping, fishing, oil extraction, etc.
Presently Arctic ice is recovering as it always does this time of year, and again Barents is notably the difference between this year and others. But a recent analysis (here) shows that it is actually the Barents Sea winter extent that is predictive of the whole Arctic ice cover.
The aim of this study is to understand and assess the predictability of the annual mean, and, in particular, the winter Barents Sea ice cover (Figure 1). We develop a prognostic framework from first principles and, based on direct observations and a 60 year simulation, assess the role of the Atlantic inflow as a main source of Barents Sea ice predictability 1–2 years in advance. Moreover, the influence and predictive potential of meridional winds on the interannual sea ice variability are investigated. (My bold)
(a) Satellite-derived (National Snow and Ice Data Center, NSIDC) mean sea ice concentration between 1980 and 2015. The ice edge (15% ice concentration) is indicated for 1980 (white line) and 2015 (black line). We confine the Barents Sea by the red line. The mooring array across the Barents Sea Opening (BSO, yellow line) is indicated by yellow circles. (b) Time series of interannual sea ice area. Annual (July–June, blue) sea ice variability is dominated by changes in winter (December–April, black) sea ice area. During winter variations in the anomalous Arctic Ocean (interior basins and surrounding shelf seas) sea ice area (green) mainly reflect the Barents Sea ice variability; the correlation between the winter sea ice area in the Barents Sea and the Arctic Ocean is 0.96, and the standard deviations are 131·103 km2 and 191·103 km2, respectively. Observed annual mean heat transport (red) shifted to the ice cover by 2 years is also shown (note reversed axis). (My bold)
Sorry to sound like a broken record, but the point is again confirmed: Oceans make the climate around the world, and in the Arctic as well. When Arctic ice varies, it is not due to fossil fuel emissions, and the proposed treaty in Paris will do nothing about it.
The authors of the study above project a lower ice extent in Barents Sea and Arctic Ocean in 2016. But presently there is a cold Blob in the North Atlantic which could change that result if it persists and signals the onset of a colder phase in that ocean.