Unprecedented summer-season sampling of the Arctic Ocean during the period 2006?2008 makes
possible a quasi-synoptic estimate of liquid freshwater (LFW) inventories in the Arctic Ocean basins.
In comparison to observations from 1992?1999, LFW content relative to a salinity of 35 in the layer
from the surface to the 34 isohaline increased by 8400 ± 2000 km3 in the Arctic Ocean (water depth
greater than 500m). This is close to the annual export of freshwater (liquid and solid) from the Arctic
Ocean reported in the literature.
Observations and a model simulation show regional variations in LFW were both due to changes
in the depth of the lower halocline, often forced by regional wind-induced Ekman pumping, and a
mean freshening of the water column above this depth, associated with an increased net sea ice melt
and advection of increased amounts of river water from the Siberian shelves. Over the whole Arctic
Ocean, changes in the observed mean salinity above the 34 isohaline dominated estimated changes in
LFW content; the contribution to LFW change by bounding isohaline depth changes was less than a
quarter of the salinity contribution, and non-linear effects due to both factors were negligible.