Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Polarstern	PS124	03.02.2021 - 30.03.2021		Weddell Sea Southern Ocean

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Hellmer Hartmut	Alfred-Wegener-Institut fur Polar- und Meeresforschung	Stanley (Falkland Islands (Islas Malvinas))	Stanley (Falkland Islands (Islas Malvinas))

Ziel der Reise / Objectives of Cruise:

PS124: Polarstern departed on 3 February 2021 from Port Stanley (Malvinas/Falkland) and steamed directly to the northern Filchner Trough region (southeastern Weddell Sea). The field work can be considered as a continuation and extension of the oceanographic, biologic, and bio-geochemical studies carried out in austral summers 2013-2014 (PS82), 2015-2016 (PS96), and 2018 (PS111). Due to a well structured station schedule, we were able to consequently translate the multi-disciplinary approach of the COSMUS cruise. We used daytime (8 am to 6 pm) mainly for mooring and Lander operations while night time was reserved for CTD (Conductivity-Temperature-Depth) profiling, water and sediment sampling, and towing the Ocean Floor Observation and Bathymetry System (OFOBS) on pre-defined tracks. A deviation from the original plan has been the circumnavigation of the new iceberg (A74) calved from Brunt Ice Shelf on 26 February 2021. Work in the Filchner Trough region ended on 16 March 2021 with the deployment of a sound-source mooring near the Stancomb-Wills-Glacier. As the onboard meteorologist predicted increasing winds at the Neumayer III Station, we stopped major parts of our scientific program in good time. After breaking through a 1-km wide compact belt of sea ice, Polarstern reached the station's northern ?pier' in the afternoon of 17 March allowing for work on the fast ice of Atka Bay by the teams of sea ice physics and physical oceanography. The loading of cargo started early in the morning of 18 March and ended in late afternoon on 19 March. The time gained due the early departure was used for the recovery of a nearby mooring despite increasing winds and higher wave crests and for moving to a new position for the deployment of a biogeochemistry mooring in the central Weddell Sea. After a calm crossing of Drake Passage Polarstern arrived at Port Stanley on 30 March 2021 at 2 pm. Important goals of the expedition PS124 (COSMUS) have been: ? Characterisation of hydrographic features and water masses of the Filchner-Ronne Outflow System, the role of bathymetry for current pathways, and the deep and bottom water formation rates at the continental slope. ? Monitoring time variations of hydrographic conditions on the eastern flank of the Filchner Trough by means of re-deployment of 3 moorings at 76?S, complemented by 3 additional moorings, and (re)- deployment of several moorings near the Filchner Trough sill in cooperation with institutes from Norway and France. ? Wide-range hydrographic profiling during austral winter west of the Filchner Trough by means of CTD- tagged Weddell Seals. ? Quantification of the Antarctic continental shelf's contribution to global carbon and nutrient/iron budgets, assessing the biological carbon pump by dissecting biotic and abiotic controls of ocean productivity and carbon exports from the surface ocean to the deep. ? Understanding and predicting the change of marine biological diversity and assessing the risk for critical transitions in marine ecosystem functionality. ? Investigation of the biological production of the Filchner Trough region and the high-energy turnover to subsequent trophic levels. ? Estimating the impact of possible changes in the hydrography and shelf and sea ice dynamics on biodiversity and ecosystem functioning of the southern Weddell Sea. ? Compilation of data on distribution patterns of pack ice seals in the Filchner Trough region. ? Describing the sea ice in front of the Filchner-Ronne Ice Shelf (FRIS) by measuring salinity, drift velocity and other physical parameters together with a sea ice buoy programme. ? Investigation of the geochemical content of the sediments. ? Measuring the micro-plastic content of seawater in the southern Weddell Sea.

Messungen / Measurements

Verankerungen / Moorings