These anomalies are very high, considering that it is now June and the melting season has only just begun.
Partly causing these high temperatures in the Arctic Ocean is water flowing into the Arctic Ocean from rivers. As the map below shows, a number of large rivers flowing through Siberia end in the Arctic Ocean.
|map from: http://en.wikipedia.org/wiki/File:Rs-map.png|
Accelerated warming of the Arctic has changed (and is still further changing) the Jet Streams, increasing the occurence of heat waves on the Norhern Hemisphere that cause huge amounts of warm water to flow into the Arctic Ocean. This is illustrated by the animation below.