The Laptev Sea as a source for recent Arctic Ocean salinity changes

This study has been motivated by observations of significant salinification of the upper Eurasian Basin that began around 1989 [Steele and Boyd, 1998] (see Figure 1 for geographical notations). Observational data and results of a coupled ice-ocean model provide evidence that increased arctic atmospheric cyclonicity in the 1990s resulted in dramatic increase of the salinity in the Laptev Sea and Eurasian Basin. Analysis of results of numerical experiments reveal two mechanisms accounting for the Laptev Sea salinization: eastward diversion of Russian rivers, and increased brine formation due to enhanced ice production in numerous leads in the Laptev Sea ice cover. The first mechanism has been also suggested earlier by Steele and Boyd [1998]. These two mechanisms were of approximately the same intensity and are linked to changes in wind patterns. The resulting Laptev Sea salinity anomaly was then advected to the central Eurasian Basin (Figure 2). The strong salinization over the Eurasian Basin altered the formation of cold halocline waters weakening vertical stratification and releasing heat from cold halocline layer upward (Figure 3). Thus, the late 1980s - 1990s processes which originated in the Laptev Sea had a dramatic impact on the thermohaline structure and circulation in the whole Arctic Ocean.

References

Steele, M., and T. Boyd, Retreat of the cold halocline layer in the Arctic Ocean, J. Geophys. Res., 103, 10419-10435, 1998.

Johnson, M. A., and I. V. Polyakov, The Laptev Sea as a source for recent Arctic Ocean salinity changes, Geophys. Res. Lett., 28, 2017-2020, 2001 [download pdf].

Figures

Figure 1. Arctic Ocean model domain. Labeled boxes denote regions for analysis of the modeling results.

Figure 2. (a) Surface (0-50m) salinity averaged over 1979-1988; (b) surface salinity anomaly for 1989-1997 showing salinization in the Laptev Sea. Contours are the associated increase in heat flux (W/m^2) from reduced vertical stratification in the upper layer.

Figure 3. Annual mean salinity anomalies for 1988-1997 in the upper 50 m of the eastern Arctic Ocean (big box in Figure 1).