ALBERT

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2017P26 drifting on Antarctic sea ice. The buoy was deployed on first year during POLARSTERN cruise PS103 (ANT-XXXII/2). The time series describes the position and additional parameters of the buoy between 10 Jan 2017 and 04 Mar 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2017P27 drifting on Antarctic sea ice. The buoy was deployed on first year ice during POLARSTERN cruise PS103 (ANT-XXXII/2). The time series describes the position and additional parameters of the buoy between 10 Jan 2017 and 03 Apr 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).

Description: Snow height was measured by the Snow Depth Buoy 2017S47, an autonomous platform, drifting on Antarctic sea ice, during POLARSTERN cruise PS103 (ANT-XXXII/2). The resulting time series describes the evolution of snow depth as a function of place and time between 10 Jan 2017 and 11 Jan 2017 in sample intervals of 1 hour. The Snow Depth Buoy consists of four independent sonar measurements representing the area (approx. 10 m**2) around the buoy. The buoy was installed on first year ice. In addition to snow depth, geographic position (GPS), barometric pressure, air temperature, and an internal ice temperature were measured. Negative values of snow depth occur if surface ablation continues into the sea ice. Thus, these measurements describe the position of the sea ice surface relative to the original snow-ice interface. Differences between single sensors indicate small-scale variability of the snow pack around the buoy. The data set has been processed, including the removal of obvious inconsistencies (missing values). Records without any snow depth may still be used for sea ice drift analyses.

Description: Snow height was measured by the Snow Depth Buoy 2017S48, an autonomous platform, drifting on Antarctic sea ice, during POLARSTERN cruise PS103 (ANT-XXXII/2). The resulting time series describes the evolution of snow depth as a function of place and time between 05 Jan 2017 and 14 Mar 2017 in sample intervals of 1 hour. The Snow Depth Buoy consists of four independent sonar measurements representing the area (approx. 10 m**2) around the buoy. The buoy was installed on attached fast ice in the Atka Bay. In addition to snow depth, geographic position (GPS), barometric pressure, air temperature, and an internal ice temperature were measured. Negative values of snow depth occur if surface ablation continues into the sea ice. Thus, these measurements describe the position of the sea ice surface relative to the original snow-ice interface. Differences between single sensors indicate small-scale variability of the snow pack around the buoy. The data set has been processed, including the removal of obvious inconsistencies (missing values). Records without any snow depth may still be used for sea ice drift analyses.

Description: The dense water flowing out from the Weddell Sea (WS), the Weddell Sea Deep Water (WSDW), significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. However, the relative importance of the western Weddell Sea as a major source region remains unclear. Several studies hypothesized that the continental shelf off Larsen Ice Shelf (LIS) is important for deep and bottom water production, but the role of the Larsen Ice Shelf remains speculative. In this work the importance of the western WS including the LIS to the production of WSDW is investigated using in situ observations and results from numerical simulations. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) in the northwestern WS add evidence to the importance of the western WS as a dense water source. An Optimum Multiparameter Analysis shows that the dense water found near the shelf break in front of the former Larsen A and B ice shelves, together with a very dense water observed off Larsen C Ice Shelf, increases the thickness and changes the θ/S characteristics of WSDW that leaves the WS through gaps in the South Scotia Ridge to form AABW. A numerical experiment performed with the Finite Element Sea-ice Ocean Model (FESOM) was used to verify the hypothesis that the continental shelf of the western WS is important for dense water formation. The model results show the changes in the thermohaline properties of the WSDW flowing along the continental slope of the western WS, as well as an increase in the transport downstream. The variability along the continental slope can be explained by fluctuations of the large-scale circulation, namely the Weddell Gyre. In addition, there is no indication that dense waters are formed in the continental shelf of the western WS, and the exchanges between continental shelf and continental slope are small. These results suggest that the area is not important for WSDW formation as previously inferred from the sparse observations mainly along the continental slope. Instead, the western WS seems to be a region where the characteristics of WSDW are determined due to mixing of waters formed upstream. Two sensitivity experiments were designed to investigate whether LIS plays an indirect role in the dense water production: (1) Larsen B Ice Shelf was added to the grid, (2) Larsen C Ice Shelf was completely removed from the grid. The experiments show that LIS plays an important role for the waters on the continental shelf but has only minor importance for the WSDW. Given the disagreement between the hypothesis derived from the observations and the model results, more in situ data are needed to determine whether the western Weddell Sea is a region where dense water is formed or whether it only serves as a conduit for dense waters formed further upstream, which interact in the western WS before reaching the final WSDW characteristics.

Description: The dense water flowing out from the Weddell Sea (WS) significantly contributes to Antarctic Bottom Water (AABW) and plays an important role in the Meridional Overturning Circulation. The larger amount of this dense water consists of Weddell Sea Deep Water (WSDW) formed in the WS, mainly in front of the Filchner-Ronne Ice Shelves and the Larsen Ice Shelf (LIS). We performed model simulations and analysis of hydrographic data that highlight the importance of the second source. Model simulations indicate that dense waters placed on the continental shelf off LIS flow down the slope and contribute to the WSDW that renews the AABW further downstream. Measurements made during the Polarstern cruise ANT XXIX-3 (2013) add evidence to the importance of the source in the western Weddell Sea. Using Optimum Multiparameter Analysis we show that the dense water found on the continental shelf in front of the former Larsen A and B together with water originating from Larsen C increases the thickness of the WSDW layer in 50%, and changes the temperature and salinity of this water mass. These modifications occur close to the WSDW outflow paths and therefore have high influence on the AABW properties.

Description: Ocean simulations performed with the Finite Element Ocean Model (FEOM) were used to show the relevance of the location of the dense water plume source on the western Weddell Sea continental shelf. When the plume starts close to the tip of the Antarctic Peninsula it flows into Bransfield Strait, but if it is found further south it can flow down the slope and contribute to Weddell Sea Deep Water (WSDW). The influence of density on the spreading was also tested indicating that a denser plume reaches greater depths while lighter plumes do not interact with the WSDW.