C036-05
Ice core studies of autumn-to-spring sea ice evolution at the MOSAiC floe
Friday, 11 December 2020: 04:16
Virtual
Marc Oggier1, Robert Rember1, Allison A. Fong2, Dorothea Bauch3,4, Dmitry Divine5, Sinhue Torres-Valdes6, Steven Fons7,8, Ellen Damm6, Hajo Eicken1, Rolf Gradinger9, Mats A Granskog5, Knut V. Høyland10,11, Ruibo Lei12, Brice Loose13, Marcel Nicolaus6, Egor Shimanchuk14, Laura Wischnewski6 and The MOSAiC Sea-Ice Biogeochemical Coring Team, (1)University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK, United States, (2)Alfred Wegener Institute Helmholtz Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (3)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (4)Leibniz-Labor, University of Kiel CAU, Kiel, Germany, (5)Norwegian Polar Institute, Tromsø, Norway, (6)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (7)University of Maryland College Park, Department of Atmospheric and Oceanic Science, College Park, MD, United States, (8)NASA Goddard Space Flight Center, Greenbelt, DC, United States, (9)UiT The Arctic University of Norway, Institute of Marine Research, Tromsø, Norway, (10)Norwegian University of Science and Technology, Trondheim, Norway, (11)The University Centre in Svalbard, Longyearbyen,, Norway, (12)Polar Research Institute of China, Key Laboratory for Polar Science of the MNR, Shanghai, China, (13)University of Rhode Island, Narragansett, RI, United States, (14)Arctic and Antarctic Research Institute, St.Petersburg, Russia
Abstract:
As a physical boundary between the atmosphere and the ocean, sea ice affects the exchange of energy and matter between them at local to hemispheric scales. Its ecological importance derives from the accumulation and transport of dissolved and particulate material, which in turn supports a broad range of organisms thriving in the ice, planktonic grazers, and higher trophic levels. However, the seasonal cycle of important physical and biogeochemical processes, and influence of sea ice processes are poorly understood, in particular in light of accelerated Arctic sea ice change.
The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) provided a unique opportunity to monitor physical, biological, and geochemical processes. During near-weekly measurements, we collected approximately 25 cores at 2 distinct sites, representing first-year and multi-year ice, respectively, to measure a wide range of properties (salinity, temperature, microstructure, chlorophyll-a, nutrients, stable isotopes, etc.).
Here we present preliminary results from the cross-disciplinary coring effort, with a focus on the growth period of the ice stratigraphy and key physical ice properties in the context of nutrient cycling and biogeochemical processes. In late Oct 2019, the first-year ice site consisted of a large area of freshly formed, undeformed 40 cm thick ice, with the upper 20 cm composed of granular ice. We observed a large fraction of air bubbles within the top 15 cm, which is correlated with low density. This pattern persisted until the end of the growth season. In early May 2020 the first-year ice grew to 1.7±0.1 m thick. The multi-year ice was collected in an area consisting of about 70-cm thick undeformed ice remnant from the previous year’s growth season and 8 cm of newly grown ice underneath. This ice grew up to 2.1±0.2 m thick by early May 2020. While we were expecting mostly columnar ice from static growth, stratigraphic observations provided evidence of platelet ice in the early stages of ice growth, indicating formation of underwater ice, possibly associated with under-ice melt ponds from the previous summer. The presence of platelet ice may not only lower the connectivity of the pore space due do jagged, interlocking crystals, but also favor the retention of nutrients and algal biomass within the ice cover.
