Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Polarstern	PS138 (ArcWatch-1)	03.08.2023 - 30.09.2023		Arctic Ocean Nansen Basin Amundsen Sea North Pole

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Boetius Antje	Alfred-Wegener-Institut fur Polar- und Meeresforschung	Troms?	Bremerhaven

Ziel der Reise / Objectives of Cruise:

The rapid warming of the Arctic and sea ice retreat affect not only the hydrography of the Arctic Ocean, but also biogeochemical and biological processes in various ways. The expedition PS138 (ArcWatch-1) investigated the biology, chemistry and physics of sea ice, as well as the impact of sea ice retreat on the entire ocean system from the surface to the deep sea. Expedition PS138 started in Troms? on August 3, 2023.The route first took us north through Norwegian waters to the ice edge and to the first ice station at 84?N and 30?E. Our journey then continued east to 83?N 130?E, and from there to the North Pole, from where we headed south again at 60?E to the ice-edge and then to our home port of Bremerhaven. We studied the dynamics of first- and multiyear ice, as well as the role of summerly ice melt and re-growth in fall for the distribution of nutrients, productivity and the composition of pelagic and benthic communities, as well as the export of particulate matter to the deep sea. During the expedition PS80 (ARK27-3, IceArc) in 2012, which took place during the largest documented sea ice minimum to date, substantial impacts on the ecosystem were found. Eleven years later, the expedition PS138 has assessed the current ecosystem state and enabled comparative studies over the timeframe of several decades. We re-visited the same locations as in 2012, and used interdisciplinary process studies to examine interactions between ice physics and biology, hydrography, biogeochemistry and biodiversity of the Arctic ecosystem, from the sea ice to the seafloor. This included comparative studies between working areas in the marginal ice zone and areas covered by multiyear sea ice in the central Arctic Ocean. The work included the deployment of a range of established and novel technologies, for example moored lander systems and towed instruments. In addition to scientific operations on the sea ice and from board, short and long-term moorings were deployed to assess the physics, chemistry and biology of the Arctic Ocean across different temporal scales. In addition, we repeated some studies at former MOSAIC sites. The results from this expedition show several anomalies in 2023 and are an important contribution to quantifying the effects of changes in sea ice cover on the Arctic Ocean and its ecosystems.

Messungen / Measurements