Ocean Dynamics DOI 10.1007/s10236-016-0988-1 Meteorology and oceanography of the Atlantic sector of the Southern Ocean—a review of German achievements from the last decade Hartmut H. Hellmer1 & Monika Rhein2 & Günther Heinemann3 & Janna Abalichin4 & Wafa Abouchami5 & Oliver Baars6 & Ulrich Cubasch4 & Klaus Dethloff7 & Lars Ebner3 & Eberhard Fahrbach1 & Martin Frank8 & Gereon Gollan8 & Richard J. Greatbatch8 & Jens Grieger4 & Vladimir M. Gryanik1,9 & Micha Gryschka10 & Judith Hauck1 & Mario Hoppema1 & Oliver Huhn2 & Torsten Kanzow1 & Boris P. Koch1 & Gert König-Langlo1 & Ulrike Langematz4 & Gregor C. Leckebusch11 & Christof Lüpkes1 & Stephan Paul3 & Annette Rinke7 & Bjoern Rost1 & Michiel Rutgers van der Loeff1 & Michael Schröder1 & Gunther Seckmeyer10 & Torben Stichel 12 & Volker Strass 1 & Ralph Timmermann1 & Scarlett Trimborn 1 & Uwe Ulbrich4 & Celia Venchiarutti13 & Ulrike Wacker1 & Sascha Willmes 3 & Dieter Wolf-Gladrow1 Received: 18 March 2016 /Accepted: 29 August 2016 # The Author(s) 2016. This article is published with open access at Springerlink.com Abstract In the early 1980s, Germany started a new era of German universities and the AWI as well as other institutes in- modern Antarctic research. The Alfred Wegener Institute volved in polar research. Here, we review the main findings in Helmholtz Centre for Polar and Marine Research (AWI) was meteorology and oceanography of the last decade, funded by the founded and important research platforms such as the German priority program. The paper presents field observations and permanent station in Antarctica, today called Neumayer III, and modelling efforts, extending from the stratosphere to the deep the research icebreaker Polarstern were installed. The research ocean. The research spans a large range of temporal and spatial primarily focused on the Atlantic sector of the Southern Ocean. scales, including the interaction of both climate components. In In parallel, the German Research Foundation (Deutsche particular, radiative processes, the interaction of the changing Forschungsgemeinschaft, DFG) started a priority program ozone layer with large-scale atmospheric circulations, and chang- ‘Antarctic Research’ (since 2003 called SPP-1158) to foster es in the sea ice cover are discussed. Climate and weather fore- and intensify the cooperation between scientists from different cast models provide an insight into the water cycle and the Responsible Editor: Jörg-Olaf Wolff * Hartmut H. Hellmer 7 Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und [email protected] Meeresforschung, Potsdam, Germany 8 GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany 1 Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany 9 A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, Russia 2 Institut für Umweltphysik IUP - Zentrum für Marine 10 Umweltwissenschaften MARUM, Universität Bremen, Institut für Meteorologie und Klimatologie, Leibniz Universität Bremen, Germany Hannover, Hannover, Germany 11 3 School of Geography, Earth and Environmental Sciences, University Environmental Meteorology, Universität Trier, Trier, Germany of Birmingham, Birmingham, UK 4 Institut für Meteorologie, Freie Universität Berlin, Berlin, Germany 12 Ocean and Earth Science, National Oceanographic Centre Southampton, University of Southampton, Southampton, UK 5 Max Planck Institut für Chemie, Mainz, Germany 13 Joint Research Centre (JRC) - European Commission’sScience 6 Department of Geosciences, Guyot Hall, Princeton, NJ 08544, USA Service, Brussels, Belgium Ocean Dynamics climate change signals associated with synoptic cyclones. MODIS Moderate-Resolution Imaging Investigations of the atmospheric boundary layer focus on the Spectroradiometer interaction between atmosphere, sea ice and ocean in the vicinity NAM Northern Annular Mode of polynyas and leads. The chapters dedicated to polar oceanog- NCEP National Centres for Environmental Prediction raphy review the interaction between the ocean and ice shelves NH Northern hemisphere with regard to the freshwater input and discuss the changes in OA Ocean acidification water mass characteristics, ventilation and formation rates, cru- P-E Precipitation minus evaporation cial for the deepest limb of the global, climate-relevant meridio- PACC Potential anthropogenic climate changes nal overturning circulation. They also highlight the associated SAM Southern Annular Mode storage of anthropogenic carbon as well as the cycling of carbon, SAMW Subantarctic Mode Water nutrients and trace metals in the ocean with special emphasis on SH Southern hemisphere the Weddell Sea. SIC Sea ice concentration SIE Sea ice extent Keywords Polar meteorology . Polar oceanography . SPP Schwerpunktprogramm (DFG Priority Program) Antarctica . Southern Ocean . Weddell Sea SZA Solar zenith angle UV Ultraviolet WDW Warm Deep Water WMO World Meteorological Organization Abbreviations WSBW Weddell Sea Bottom Water AABW Antarctic Bottom Water WSDW Weddell Sea Deep Water AAIW Antarctic Intermediate Water AAO Antarctic Oscillation ABS Amundsen-Bellingshausen Sea 1 Introduction ACC Antarctic Circumpolar Current AMPS Antarctic mesoscale prediction system Two hundred years ago, the Southern Ocean was viewed as an AOGCM Atmosphere-ocean general circulation model inaccessible, stormy and icy sea, challenging dauntless explorers, AWI Alfred Wegener Institute Helmholtz Centre for hunters and whalers. Today, the Southern Ocean is considered to Polar and Marine Research be an important tessera of the climate puzzle hosting numerous CAO Cold air outbreak processes of global importance. It connects the three major CBL Convective boundary layer oceans through the most vigorous ocean current on Earth, the CDW Circumpolar Deep Water Antarctic Circumpolar Current, ventilates most of the world CFC Chlorofluorocarbon ocean abyss, participates in the global carbon cycle and affects COSMO Consortium of small-scale modelling the rate of global sea level rise due to the interaction with the CTD Conductivity-temperature-depth Antarctic Ice Sheet. However, the Southern Ocean not only acts DFG Deutsche Forschungsgemeinschaft (German but also reacts to sea floor topography and the polar atmosphere. Research Foundation) The former guides currents around the continent, warm waters of DOC Dissolved organic carbon open ocean origin into ice shelf cavities, dense shelf waters down DOM Dissolved organic matter the continental slope and determines the kind of water able to DWD German Meteorological Service escape the basins of the marginal seas. The latter provides energy ECHAM General circulation model of the Max Planck for driving the ocean currents, controls the surface fluxes of heat Institute for Meteorology (Hamburg) and moisture, regulates the exchange of natural and anthropo- EMAC ECHAM/MESSy Atmospheric Chemistry genic gases and determines sea ice properties and coverage with ERA ECMWF reanalysis consequences for primary production, ocean-air fluxes and water ETC Extra-tropical cyclone mass characteristics. The atmosphere links air-ice-ocean interac- FESOM Finite Element Sea ice Ocean Model tion with the stratosphere, e.g. changes in stratospheric circula- FRIS Filchner-Ronne Ice Shelf tion, due to ozone loss, to tropospheric circulations and sea ice GHG Greenhouse gas coverage. Furthermore, the atmosphere is the fastest connection HIRHAM Regional climate model combining HIRLAM between Antarctica and the mid-latitudes, and the tropics. and ECHAM It is the interplay between both components of the climate HIRLAM High-resolution limited area model system, which restricts scientific surveys in the Southern HSSW High-Salinity Shelf Water Ocean mainly to the austral summer season, and even then, LES Large Eddy Simulation the access to the continental shelves of the marginal seas is LIS Larsen Ice Shelf limited. The combination of results from the few expeditions Ocean Dynamics to the Antarctic coast, the increasing capability of satellite months. Two research aircraft are available for scientific cam- sensors, and the progress achieved in terms of numerical mod- paigns during the summer season. These research platforms el development revealed that the continental shelves are the (stations, icebreaker, aircraft) are run by the Alfred Wegener prime locations for sea ice formation due to intense ocean heat Institute Helmholtz Centre for Polar and Marine Research loss to the cold atmosphere. Concentrated in coastal polynyas, (AWI) and allow the operation of modern devices ranging the resulting brine rejection causes a densification of the con- from ROVs to recently used unmanned air vehicles (UAV, tinental shelf water. This water mass either contributes to the Jonassen et al. 2015) for atmospheric boundary layer research. formation of deep and bottom water or participates in the sub- Here, we review the achievements of recent investigations ice shelf circulation providing the heat for basal melting. The of the polar atmosphere and ocean with the focus on the meltwater input influences the stability of the shelf water col- Weddell Sea, primarily funded by the Priority Program umn with consequences for sea ice cover, for air-sea fluxes (Schwerpunktprogramm, SPP-1158) ‘Antarctic Research’ of and for the characteristics of the deep and bottom waters. The the German National Science Foundation (Deutsche main source region for both water masses is the southern ex- Forschungsgemeinschaft, DFG). The main aim of the SPP is treme of the Atlantic Ocean, the