Abstract:

Using seal CTD data obtained in Vincennes Bay (Antarctica) during March–October 2012, this study investigated the evolution of water structure on the continental shelf under the influence of the intrusion of modified Circumpolar Deep Water (mCDW) during the freezing period. Results showed obvious mCDW intrusion in the deep layer from the bay mouth to the innermost part of the bay. Effects from cooling and brine rejection during sea ice formation extended from the upper layer into the interior; however, deep layer (>400 dbar) stratification in the innermost part of the bay remained unbroken until mid-June. Under the different influences of heat brought by mCDW, the glacier front C-Zone and the polynya D-Zone of the innermost bay exhibited different water structure characteristics. From early April to June, Ice Shelf Water (ISW) persisted at depths of 300–600 dbar in the C-Zone with warm cores (θ > −1.7°C) above and below, indicating that the heat carried by mCDW causes melting of the ice shelf within this depth range, while the meltwater of the ice shelf cools the seawater. Ocean heat content in the D-Zone was substantially higher than that in the C-Zone, and ISW was found below 400 dbar only in early April. Therefore, mCDW carries more heat into the D-Zone, and melting of the ice shelf in the D-Zone might occur over a deeper range. Additionally, during the late freezing period (September – October), the vertical characteristics of the water in polynyas tend to be homogeneous, proving the existence of deep convection for the formation and accumulation of Dense Shelf Water.

Key words: modified Circumpolar Deep Water, Ice Shelf Water, polynya, evolution of water structure, Antarctica, Vincennes Bay