Halocline water modification and along-slope advection at the Laptev Sea continental margin

[摘要] A general pattern in water mass distribution and potential shelf–basinexchange is revealed at the Laptev Sea continental slope based onhydrochemical and stable oxygen isotope data from the summers 2005–2009. Despiteconsiderable interannual variations, a frontal system can be inferredbetween shelf, continental slope and central Eurasian Basin waters in theupper 100 m of the water column along the continental slope. Net sea-icemelt is consistently found at the continental slope. However, the sea-icemeltwater signal is independent from the local retreat of the ice cover andappears to be advected from upwind locations.

In addition to the along-slope frontal system at the continental shelfbreak, a strong gradient is identified on the Laptev Sea shelf between122° E and 126° E with an eastward increase of riverineand sea-ice related brine water contents. These waters cross the shelf breakat ~ 140° E and feed the low-salinity haloclinewater (LSHW, salinity S < 33) in the upper 50 m of the water column.High silicate concentrations in Laptev Sea bottom waters may lead tospeculation about a link to the local silicate maximum found within thesalinity range of ~ 33 to 34.5, typical for theLower Halocline Water (LHW) at the continental slope. However brine signatures andnutrient ratios from the central Laptev Sea differ from those observed atthe continental slope. Thus a significant contribution of Laptev Sea bottomwaters to the LHW at the continental slope can be excluded. The silicatemaximum within the LHW at the continental slope may be formed locally or atthe outer Laptev Sea shelf. Similar to the advection of the sea-ice meltsignal along the Laptev Sea continental slope, the nutrient signal at 50–70 mwater depth within the LHW might also be fed by advection parallel to theslope. Thus, our analyses suggest that advective processes from upstreamlocations play a significant role in the halocline formation in the northernLaptev Sea.

[学科分类] 海洋学与技术