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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
idw - Informationsdienst
Wissenschaft
With the departure of the research vessel Polarstern from Punta Arenas (Chile) scheduled for this weekend, the "Summer Weddell Sea Outflow Study" (SWOS) international expedition will commence. Up to early April, a multidisciplinary international research team will investigate the northwestern region of the Weddell Sea – an area of central importance for the global climate and ocean system, but one that can only be explored on site by research icebreakers such as the Polarstern due to challenging sea ice conditions.
For a long time, the sea ice extent in Antarctica was observed to be relatively stable – unlike in the Arctic, where the summer ice extent has shrunk by around 12 per cent per decade since satellite records began in 1979. As from around 2017, however, significant changes have been observed in the north-western Weddell Sea: the summer sea ice extent has declined sharply, presumably as a result of warmer surface water. “The aim of SWOS is to investigate why sea ice in Antarctica has declined so sharply in recent years and how this is impacting the ecosystem,” as Prof. Dr Christian Haas from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) stated, who is leading the current Polarstern expedition. At the same time, the sea ice physicist reports that an unexpected situation has arisen this year: “Ironically, there is currently an unusually large amount of ice in the western Weddell Sea, which may be a normal fluctuation without contradicting the trend. Consequently, it remains to be seen whether we will be able to penetrate deep into the south as planned – meaning that we will adapt our questions to the prevailing conditions en route and develop them accordingly.”
AWI marine biologist Dr Ilka Peeken, co-leader of the expedition, also emphasises the planning challenges: given that the northern part of the working area is less open than in previous years, routes will have to be adjusted flexibly. “It is currently unclear whether we will be able to reach the vicinity of the Larsen C Ice Shelf as planned,” says Ilka Peeken. Nevertheless, she adds, the expedition is a rare opportunity to penetrate a region that has hardly been studied directly to date. The north-western Weddell Sea is situated along the northward-flowing Weddell Gyre, which transports large quantities of different water masses and thick sea ice into the world's oceans. In addition, icebergs calving from the ice shelf carry nutrients from the Antarctic continent into the ocean, where they impact on biogeochemical cycles. The region includes a deep shelf sea and the Larsen C Ice Shelf, the second largest ice shelf in the Weddell Sea. In spite of its global significance, actual knowledge of the Larsen Ice Shelf is patchy due to the fact that the year-round ice cover, often multi-year sea ice, as well as the extreme weather conditions make access difficult.
The SWOS expedition aims to collect comprehensive observations for the first time from the seabed to the atmosphere along the northwestern Weddell Sea continental slope, on the shelf and in the vicinity of the Larsen C Ice Shelf. The focus is on the interactions between sea ice, ice shelves and the ocean, as well as their impacts on hydrography, nutrient balance and carbon fluxes. The research team is recording ecological processes in the ice and on the seabed, as well as ecological gradients depending on sea ice conditions. In addition, the regional sea ice thickness distribution and snow properties will be measured, water masses characterised and exchange processes between the shallow shelf and deep-sea basins investigated.
“It is not possible to answer many of our questions by satellites alone,” explains Christian Haas. We need in-situ observations to understand the state of the sea ice, the currents and the biological communities in the water and on the seabed – as well as to be able to assess whether the sea ice could possibly disappear entirely in the near future.” The collected data will also be used to improve satellite-based sea ice observations.
The research is taking place at a critical time, when the Antarctic climate system may be entering a phase of accelerated sea ice loss and increasing ocean warming. “We are operating in a region that has been shaped by the earlier ice shelf collapses of Larsen A and B, as well as recent changes to Larsen C,” says Ilka Peeken. “It is precisely under these conditions that we have the opportunity to obtain key data on biodiversity changes, ocean currents and sea ice conditions in the Weddell Sea.” The results will be incorporated into ongoing long-term studies, while serving as future projections of the Antarctic system and thereby contributing to the further development of Earth System Models.
A wide range of modern and conventional measurement systems are being deployed, including helicopters to measure sea ice thickness, microstructure probes, CTD rosettes, various trawls and bottom sampling and observation devices, as well as autonomous platforms. “I am very much looking forward to investigating the extent to which the ice in the north-western Weddell Sea has changed. I first visited the region over 30 years ago, and seven years ago I was there for the last time with the Polarstern when the sea ice began to change,” as Christian Haas relates. For Ilka Peeken, the close interconnection between the disciplines is the most exciting aspect of the expedition: “Although this region is one of the most inhospitable on Earth, it is teeming with life. Investigating the contribution of the sea ice ecosystem to the carbon cycle is a particular highlight for me.”
The SWOS expedition is intended to make decisive contributions to understanding a key area of the Antarctic ice-ocean system – at a time of profound change whose effects extend far beyond Antarctica. On concluding the expedition, the Polarstern will embark on its return journey across the Atlantic. The voyage will be used for student training and is scheduled to wind up in Bremerhaven in mid-May.
Prof Dr Christian Haas, christian.haas@awi.de
Dr Ilka Peeken, ilka.peeken@awi.de
https://www.awi.de/en/about-us/service/press.html Press release&pictures
https://follow-polarstern.awi.de/ Polarstern-App
https://we.tl/t-1sKGGvRveo Video
Polarstern in the western Weddell Sea
Quelle: Ilka Peeken
Copyright: Alfred Wegener Institute / Ilka Peeken
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