Off You Go, Polarstern!

On 20 September 2019, the German research icebreaker Polarstern departs from Tromsø, Norway, to spend an entire year drifting through the Arctic Ocean, trapped in sea ice. A total of six hundred people from 19 countries will participate in the expedition. The data gathered during six cruise legs, covering full polar night and polar day conditions and everything in between, will be used by numerous researchers to take climate and ecosystem research to a next level.

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will be the first year-round expedition into the central Arctic exploring its climate system. It is the largest Arctic expedition following the concept of Fridtjof Nansen’s Fram expedition in 1893. The project with a total budget exceeding 120 Million Euro has been designed by an international consortium of leading polar research institutions, under the umbrella of the International Arctic Science Committee (IASC), led by the German Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), the Russian Arctic and Antarctic Research Institute (AARI) and the University of Colorado, Cooperative Institute for Research in Environmental Sciences (CIRES), United States. RV Polarstern will serve as the central observatory, drifting with the sea ice across the central Arctic towards Fram Strait for a year. A distributed regional network of observational sites will be set up on the sea ice in an area of up to ~50 km distance from RV Polarstern. The ship and the surrounding network will drift with the natural ice drift across the polar cap towards the Atlantic, while the sea ice thickens during winter.

Link between MOSAiC and YOPP
A strong link between MOSAIC and YOPP has existed right from the beginning of MOSAiC’s planning. "Both projects strive to better understand the Arctic climate system", explains expedition leader Markus Rex in his interview with PolarPredictNews (see PolarPredictNews #12). "MOSAiC has always been considered one of the key projects contributing to the Year of Polar Prediction", says PPP Steering Group chair Thomas Jung. MOSAiC is thus also one of the first projects which received endorsement by the Year of Polar Prediction in late 2015, as it 'supports YOPP by the evaluation of near-real-time observational data in a long-term context'. Ever since, MOSAiC planning has involved YOPP as an important partner.

MOSAiC – A YOPP Supersite
The MOSAiC central observatory and the surrounding distributed network of instruments will serve as a YOPP Supersite. Together with other YOPP Supersites, MOSAiC observational data will be used within the YOPPSiteMIP project led by PPP Steering Group members Gunilla Svensson from Stockholm University and Taneil Uttal from the U.S. National Oceanic and Atmospheric Administration. Measurement procedures will be standardized for all observational YOPP Supersites including  MOSAiC in order to compare instrumental observations with model data output at high frequency. This will enable multimodel and multisite verification and process evaluation until the end of the Polar Prediction Project in 2022, and beyond.

Third Arctic Special Observing Period
A third Arctic Special Observing Period is planned during MOSAiC, tentatively scheduled from December 2019 through April 2020. This third Arctic SOP-NH3 will have a focus on improving observational coverage during episodes of strong interactions between the Arctic and mid-latitudes. These are i) warm air intrusions being associated with the mid-latitudes driving Arctic weather and climate and ii) cold-air outbreaks which are episodes when the Arctic has strong influence on mid-latitude weather. This third SOP in the Arctic will thus be different from the previous SOPs as additional radiosonde launches and other measurements will only focus on key regions. The most prominent third SOP region is of course the central Arctic Ocean with RV Polarstern and the surrounding distributed instrument network.

Sea-Ice Drift Forecast Experiment
Another major link between YOPP and MOSAiC has been established by the implementation of the Sea-Ice Drift Forecast Experiment (SIDFEx). A central component of this YOPP activity is the provision of near-real-time ice drift forecasts for the MOSAiC site from several operational forecast centers. The forecasts will be made available on the ship and on a land-based server, openly accessible through an interactive online tool at The forecasts are meant to support the ordering of satellite imagery and logistics in the field, and to provide an additional basis for forecast system evaluation.

International YOPP Participation in MOSAiC
Different members of the PPP Steering Group will either participate themselves, send colleagues aboard or will be involved elsewise with MOSAiC.

Environment and Climate Change Canada (ECCC) plans to use observations collected during MOSAiC for a variety of studies to improve coupled environmental prediction to support the YOPPSiteMIP and SIDFEx efforts. The unique location of MOSAiC observations and co-localization of atmosphere, sea-ice and ocean observations will be used by ECCC to improve boundary layer parameterization as well as fluxes across the sea-ice interface. In addition, ECCC is proving a real-time stream of graphical products from the Canadian Arctic Prediction System (CAPS) being run for YOPP. These products are shared with scientists aboard Polarstern for planning of field campaign activities and research efforts.

The Polar Observations and Processes Group from the U.S. National Oceanic and Atmospheric Administration (NOAA) will provide off-site support sea-ice forecasting activities for Polarstern, in addition to their contribution to SIDFEx.  They will also support the YOPPSiteMIP project by creating standardized files from the MOSAiC expedition that can later be used for the model evaluation.

Colleagues from the Chinese National Marine Environmental Forecasting Center (NMEFC) will work with the observational data to simulate the sea-ice evolution during MOSAiC by a sea-ice column model. NMEFC will also run operational weather and sea-ice forecasts during MOSAiC.

In-Situ Observations
In-situ sea-ice observations by colleagues from Dartmouth College, New Hampshire, USA, will be complemented by the deployment of four autonomous seasonal ice mass balance buoys which measure air, snow, ice, and ocean temperature profiles as well as snow deposition and melt, ice growth, ice surface and bottom melt. These observations are designed to help ‘scale up’ the measurements at the MOSAiC Central Observatory (kilometers) to the distributed instrument network (tens of kilometers).

In support of MOSAiC and YOPP, the Arctic and Antarctic Research Institute (AARI) in St. Petersburg, Russia, will deploy four to five synoptic meteorological buoys during the MOSAiC drift in October 2019 in the Eurasian Arctic (Laptev Sea, East Siberian Sea) and potentially in spring 2020 in the Barents Sea and the Arctic Basin.

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