The bulge is some 8,000 cubic km in size and has risen by about 15cm since 2002. The team thinks it may be the result of strong winds whipping up a great clockwise current in the northern polar region called the Beaufort Gyre. https://climatestate.com/2013/08/07/does-freshwater-runoff-in-the-arctic-change-ocean-circulation-to-unlock-methane-hydrate-in-the-deep-ocean/