Cross‐shelf transport of warm and saline water in response to sea ice drift on the Laptev Sea shelf

Abstract

are used to describe recent changes in the Laptev Sea hydrography and to highlight wind-and ice-driven surface Ekman transport as the mechanism to translate these changes from the outer-to the inner-shelf bottom waters. In February 2010, moored oceanographic instruments recorded a sudden increase in temperature (+0.8 C) and salinity (+ >3) near the bottom of the inner Laptev Sea shelf. Such warm and saline waters had not been previously observed on the inner shelf in winter. They likely originated from the basin and were first observed during a summer 2009 CTD survey in the northwestern shelf break region, subsequently spreading east and shoreward across the Laptev Sea shelf. The changes were introduced to the mooring site by the first of a series of bottom-intensified flow events with velocities reaching 20 cm s À1 , topographically guided along a relic submarine river valley. Each of the flow events coincided with negative pressure anomalies at the mooring site and offshore-directed (upwelling-favorable) winds and ice drift. We suggest that the observations to first order resemble a simplified two-dimensional two-layered ocean, where offshore surface Ekman transport is compensated for by a barotropic shoreward response flow near the bottom. In this paper, we use one of the first comprehensive long-term Laptev Sea datasets to highlight ice-ocean-atmosphere interactions in early and late winter and discuss the role of freshwater, stratification, and ice mobility on under-ice circulation on the Laptev Sea shelf.Citation: Janout, M. A., J. Ho¨lemann, and T. Krumpen (2013), Cross-shelf transport of warm and saline water in response to sea ice drift on the Laptev Sea shelf,

Seasonal and interannual variability of fast ice extent in the southeastern Laptev Sea between 1999 and 2013

“…Air temperatures and oceanic heat control sea ice growth rates and hence, the time needed to reach an ice thickness of 5–10 cm by thermodynamic growth, which is required to withstand external stresses. While year‐round mooring observations from the deeper (>40 m) Laptev Sea shelf show surface warmed waters that may be trapped in the interior water column into fall and winter [ Janout et al ., ], significant amounts of heat were not observed in the shallower waters within the fast ice zone. Bauch et al .…”

Circulation in the northwest Laptev Sea in the eastern Arctic Ocean: Crossroads between Siberian River water, Atlantic water and polynya‐formed dense water

“…The ADCPs recorded hourly ensembles using 1 m (300 kHz) and 4 m (150 kHz) bins. The 300 kHz ADCP's compass headings from the sea ice drift is in good agreement with satellite sea ice drift (see section 2.3), which gives us good confidence regarding the quality of upper ocean current directions [ Janout et al ., ]. The principle current components from the nearest bins between the two ADCPs are in near‐perfect agreement except that they are offset by 55°, which we assume constitutes an offset in the 150 kHz ADCP's compass.…”

Kara Sea freshwater transport through Vilkitsky Strait: Variability, forcing, and further pathways toward the western Arctic Ocean from a model and observations

“…Nearly 50% of the Arctic river water enters from three of the largest rivers on earth over the vast Kara and Laptev Sea shelves from the Lena (531 km 3 a −1 ), Ob (412 km 3 a −1 ), and Yenisey (599 km 3 a −1 ; Figure ) [ Dai and Trenberth , ]. The discharge is highly seasonal (Figure ) and controls the summer stratification [ Janout et al ., ] and biogeochemical environment on the Siberian shelves [ Holmes et al ., ]. The distribution and fate of the river plumes is primarily dominated by winds in summer [ Dmitrenko et al ., ].…”