KIT’s “Atlas of Antarctic Sea Ice Motion” now added to the data and information portal meereisportal.de
8 March 2021
Continuous datasets from the polar regions are valuable witnesses of the climate change that has become increasingly apparent around the globe since the 1980s. These include data on sea-ice formation and dynamics in the Antarctic pack-ice belt. When the Federal Republic of Germany became a signing member of the Antarctic Treaty in 1979 and established the Georg-von-Neumayer Station, an Antarctic station operated year-round, the stage was set for gathering regular readings in this normally hard-to-access region.
In 1986, several years after the Georg-von-Neumayer Station commenced operations, in the context of the Winter Weddell Sea Study the research icebreaker Polarstern began deploying automatic monitoring buoys in the winter sea ice of the Antarctic. Although researchers from the German Democratic Republic (GDR) had previously done fieldwork in the Antarctic, they hadn’t pursued this avenue. Before that, US researchers had begun gathering the first buoy-based measurements in the Weddell Sea in 1978. The specially reinforced ice buoys for meteorological, oceanographic and in some cases sea ice / glaciological measurements offered a new means of gathering essential information on temperatures in the atmosphere, ice/snow and water, and on ice movement and wind, even in remote sea-ice-covered regions.
Since Australian, US, Finnish, Norwegian, British and Italian groups had by now begun gathering similar measurements, internationally coordinating buoy deployment, data collection and data exchange simply made good sense. This was achieved in the form of the new International Project on Antarctic Buoys (IPAB) (with Christoph Kottmeier, at the time affiliated with the AWI / University of Bremen, as its Speaker), part of the World Climate Research Programme (WCRP), starting in ca. 1990. Although the IPAB was similar to the Arctic buoy programme IABP in terms of the basic idea, it proved harder to implement: the nature of ice movement in the Antarctic often produced divergent shifts between the ice and the buoys installed on it on the one hand, and the surrounding oceans on the other; as a result, many units broke down or were destroyed. In contrast, the nearly seamless ice of the Arctic Basin means considerably longer operating times for sea-ice buoys, not to mention being far better suited to the deployment of simple buoys from aircraft. Given the fact that Antarctic sea ice virtually disappears in the summer, and given the mechanical strains within the increasingly thin ice, buoys deployed there usually only survive for a few months to a year.
Despite these difficulties, by 1997 a sizeable dataset of unique in-situ measurements had accumulated, though the content had never been systematically compiled. For many local and regional studies, the ice-drift data offered a host of new insights into ice dynamics under the influence of wind and ocean currents; into polynya formation along coastlines and out to sea; and into thermal transfer and ice formation. However, due to the gaps in its spatial and chronological coverage, the ice drift data gathered from satellite-tracked buoys wasn’t enough to draw any general conclusions regarding circum-Antarctic kinematics and dynamics.
In this context, applying modern methods from the microwave-based remote sensing of sea ice (SSMR, SSM/I) proved to offer an excellent solution. These methods are based on pattern recognition and tracking for typical structures on a scale of ca. 10 km. The data was prepared and made available by NASA’s JPL (Dr M. Drinkwater and his team). In addition, the so-called reanalyses of meteorological data provided by the European Centre for Medium-Range Weather Forecasts (ECMW) were drawn on, especially with regard to wind fields.
After Christoph Kottmeier switched from the AWI / University of Bremen to what is now the KIT in 1997, DFG project funding secured at the KIT presented an opportunity to comprehensively compare and combine the in-situ buoy data, the remote sensing data on sea-ice movement, and the reanalysis data from the ECMW. The spatial movement fields and many other variables, which have a chronological resolution of only several days, covered the Antarctic (circumpolar) from 1978 to 1997 with a spatial resolution of several kilometres. In addition, several derived parameters, e.g. the “differential kinematic properties” of ice movement (rotation, divergence and shearing) were calculated. Both the numerical data and an extensive range of presentation options to choose from were made publicly available online in the Atlas of Antarctic Sea Ice Motion. The analyses were used e.g. in a dissertation (Dr Carolin Schmitt) and a host of international publications. “The Atlas is certainly an important basis for the highly topical discussions regarding climate change in the Antarctic,” says Christoph Kottmeier with regard to the Atlas’s significance today.
Yet, when Kottmeier retired in 2020, it could no longer be guaranteed that the data would remain available at the KIT. As such, it was a happy coincidence that the AWI and KIT, as fellow Helmholtz Centres, had already established close collaborations, through e.g. the four regional Helmholtz Climate Offices, the Helmholtz Climate Initiative “Regional Climate Change” (REKLIM) and, from 2021, through the joint Helmholtz research programme The Changing Earth, allowing them to collaborate and pool their resources. The KIT’s Atlas of Antarctic Sea Ice Motion was subsequently prepared for its new role as a permanent resource available at the AWI’s meereisportal.de, which will also make it possible to combine it with other datasets from after 1998 in the future. You can access the Atlas here.
“But what this really achieved was to permanently safeguard valuable datasets on the recent history of Antarctic research, ensuring that these datasets will be available for future generations of researchers to come,” underscores Dr Renate Treffeisen from the Alfred Wegener Institute in Bremerhaven. According to her colleague Dr Klaus Grosfeld: “The data can be used, for example, to validate sea-ice models, to assess climatic changes in the Southern Ocean, and for the further investigation of small-scale processes like local sea-ice dynamics, polynya formation and tidal effects.”
Atlas of Antarctic Sea Ice Motion
Interannual variability in Antarctic sea ice motion. Interannuelle Variabilität antarktischer Meereis-Drift; Schmitt, Carolin, 2006. ISSN: 0179-5619.
Prof Dr Christoph Kottmeier (KIT)
Dr Klaus Grosfeld (AWI)
Dr Renate Treffeisen (AWI)