Impact of Siberian coastal polynyas on shelf‐derived Arctic Ocean halocline waters

Abstract

18 O correlation showed well-defined mixing lines for bottom and surface layers. In March-April 2009, surface waters were strongly influenced by Lena River water, and local polynya activity with elevated brine signals reached to intermediate depth but did not penetrate the bottom layer in the highly stratified water column. Inventory values of sea ice formation were comparable in both years, but freshwater distributions from the preceding summers were different. Therefore, the observed difference in the impact of polynya activity on the water column is not primarily controlled by the amount of sea ice formed during winter but by preconditioning from the preceding summer. Only in years when the river plume is mostly absent in the polynya region is stratification weak and allows winter sea ice formation to reach the bottom layer. Thus summer stratification controls the influence of local polynya water on the shelf's bottom hydrography and, as bottom water is exported, impacts on the source water of shelf-derived halocline waters.

Correlation of river water and local sea‐ice melting on the Laptev Sea shelf (Siberian Arctic)

“…In winter, sea‐ice formation transports river water (f r ) from the surface to intermediate depth and into the bottom layer [ Bauch et al ., ]. Therefore, the whole water column is dominated by a negative f SIM /f r correlation in winter, and the average winter surface layer has a river water content of ~30 ± 10% [ Bauch et al ., ]. In the consecutive summer, the surface layer is altered by river discharge and sea‐ice melting and dominated by a positive f SIM /f r correlation (see solid line in Figure ).…”

“…To identify sea‐ice melting of the current summer, the preconditioning from the previous winter has to be known. In winter, sea‐ice formation transports river water (f r ) from the surface to intermediate depth and into the bottom layer [ Bauch et al ., ]. Therefore, the whole water column is dominated by a negative f SIM /f r correlation in winter, and the average winter surface layer has a river water content of ~30 ± 10% [ Bauch et al ., ].…”

“…In the consecutive summer, the surface layer is altered by river discharge and sea‐ice melting and dominated by a positive f SIM /f r correlation (see solid line in Figure ). Nevertheless, the winter preconditioning is still preserved in the bottom layer (see stippled line in Figure ) and reflects past winter polynya activity [ Bauch et al ., ]. Interannual comparison shows some variations in absolute values and ranges of f SIM and f r values, but the negative f SIM /f r ratio in the bottom layer is found constant for all investigated years (see closed symbols in Figure ).…”

Baseline Monitoring of the Western Arctic Ocean Estimates 20% of Canadian Basin Surface Waters Are Undersaturated with Respect to Aragonite

“…The gray points show the data from Figure 8. For the freshwater end-member [33], [35], [39], [55], TA MW  = 1000 µmol kg −1 , S FW  = 0, and T CO 2MW  = 940 µmol kg −1 . For the sea ice meltwater end-member [40], [71], TA SIM  = 540 µmol kg −1 , S SIM  = 4, and T CO 2SIM  = 300 µmol kg −1 .…”

“…[40]). We calculate the δ 18 O value of sea ice from the δ 18 O value measured in the local surface water plus a fractionation factor for liquid–solid water isotopic fractionation: δ 18 O SIM  = δ 18 O measured +2.6‰ [33], [41]. Each cruise measurement of δ 18 O therefore provides an individual estimate of δ 18 O SIM .…”