Changes in distribution of brine waters on the Laptev Sea shelf in 2007

Combined salinity and delta O-18 data from summer 2007 reveal a significant change in brine production in the Laptev Sea relative to summer 1994. The distribution of river water and brine-enriched waters on the Laptev Sea shelf is derived based on mass balance calculations using salinity and d18O data. While in 1994 maximal influence of brines is seen within bottom waters, in 2007 the influence of brines is highest within the surface layer and only a moderate influence of brines is observed in the bottom layer. In contrast to 2007, salinity and delta O-18 data from summer 1994 clearly identify a locally formed brine-enriched bottom water mass as mixing end-member between surface layer and inner shelf waters on one side and with higher salinity water from the outer Laptev Sea on the other side. In 2007, the brine-enriched waters are predominantly part of the surface regime, and the mixing end-member between surface layer and outer shelf waters is replaced by a relatively salty bottom water mass. This relatively salty bottom water probably originates from the western Laptev Sea. The inverted distribution of brines in the water column in 2007 relative to 1994 suggests a less effective winter sea ice formation in winter 2006-2007 combined with advection of more saline waters from the western Laptev Sea or the outer shelf precedent to the climatically extreme summer 2007. The observed changes result in an altered export of waters from the Laptev Sea to the Arctic Ocean halocline.