The bulge is some 8,000 cubic km in size and has risen by about 15cm since 200
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.
This would force the water together, raising sea surface height, the group tells the journal Nature Geoscience.
"In the western Arctic, the Beaufort Gyre is driven by a permanent anti-cyclonic wind circulation. It drives the water, forcing it to pile up in the centre of gyre, and this domes the sea surface," explained lead author Dr Katharine Giles from the Centre for Polar Observation and Modelling (CPOM) at University College London.
"In our data, we see the trend being biggest in the centre of the gyre and less around the edges," she told BBC News.
Dr Giles and colleagues made their discovery using radar satellites belonging to the European Space Agency (Esa).
BBC
