Emerging physical and biological properties in a new Arctic ice regime

Transcription

1 Emerging physical and biological properties in a new Arctic ice regime Philipp Assmy 1, Mar Fernández-Méndez 1, Lasse Mork Olsen 1, Hanna M. Kauko 1, Pedro Duarte 1, Polona Itkin 1, Amelie Meyer 1, CJ Mundy 2, Samuel R. Laney 3, Agneta Fransson 1, Haakon Hop 1,4, Ioanna Merkouriadi 1, Anja Rösel 1, Achim Randelhoff 1,4, Alexey K. Pavlov 1, Anette Wold 1, Jozef M. Wiktor 5, Geir Johnsen 6, Sebastian Gerland 1, Brian Sorrell 7, Arild Sundfjord 1, Harald Steen 1 and Mats A. Granskog 1 1 Norwegian Polar Institute, Norway 2 University of Manitoba, Canada 3 Woods Hole Oceanographic Institution, USA 4 UiT The Arctic University of Norway, Norway 5 Institute of Oceanology Polish Academy of Sciences, Poland 6 Norwegian University of Science and Technology, Norway 7 Aarhus University, Denmark Picture: P. Leopold Arctic Frontiers, Tromsø, 24 January 2018

2 Emerging physical properties of the new Arctic icescape Thinner Younger More dynamic March Winter sea ice mean montion Perovich et al Arctic Report Card; Kowk et al JGR: Oceans

3 Sneak preview of the future Seasonal Ice Zone Meereisportal.de Yermak Plateau Nansen Basin 15. January June 2015 Itkin et al. «Direct observations of atmosphere -- sea ice -- ocean interactions during Arctic winter and spring storms Svalbard The new Arctic in the global context - Observation Part 1 Thursday 25 January 09:45 Drift Floe 1 Floe 2 Floe 3 Floe 4 Season Winter Winter Spring Spring/Summer Duration (days) Air temperature -27.4C -13.7C -10.1C -0.4C Ice thickness 1.0/1.7m 1.3m 1.6m 1.4m Snow thickness 0.3/0.5m 0.55m 0.5m 0.3m Major storms N-ICE2015 special issue in JGR:

4 Under-ice phytoplankton bloom 12 May 12 May 26 May 26 May PSW=Polar Surface Water AW=Atlantic Water CJ Mundy Assmy et al Scientific Reports The weak re-circulation pattern over YP implies that the bloom grew in situ beneath the ice pack

5 Under-ice phytoplankton blooms Pre-melt season Phaeocystis Meereisportal.de May 2015 Assmy et al Scientific Reports CJ Mundy Diatoms Meereisportal.de Melt season Laney & Sosik 2014 DSR II July 2011 Arrigo et al Science

6 Pressure ridges up to 51% of the area studied was deformed ice (including ridges and rubble ice) Photo: Vasily Kustov and Sergey Semenov (Arctic and Antarctic Research Institute, St. Petersburg, Russia)

7 Pressure ridges: biological hotspots Nitzschia frigida Thalassiosira bioculata 50 µm Fernández-Méndez et al., in revision Front Mar Sci Pressure ridges are biological hotspots (Syvertsen 1991; Hegseth 1992; Hop et al. 2000; von Quillfeldt et al. 2009; Gradinger et al. 2010) and contribute significantly to ice algal standing stocks, particularly during the summer melt season.

8 Multi-year ice algal repository 1 Summer FYI Exchange of ice algae Repository building 2 Fall/Winter Release of ice algal aggregates Loss of MYI might compromise seeding of the ice algal spring bloom MYI Closed brine channels Picture: Philipp Assmy 3 Spring Ice growth 50 cm Ice melt MYI FYI YI Ice-algal bloom Release of ice algae Nitzschia frigida Single cells Arborescent colonies Aggregates Seeding of FYI and YI by MYI Olsen et al JGR

9 «Antarctification» of the Arctic ice pack in the Atlantic sector 130 mg Chl a m -3 Fernández-Méndez et al. in revision Front Mar Sci 20 µm Snow infiltration communities have been frequently reported from the Antarctic but few reports from the Arctic (Buck et al. 1998, McMinn&Hegseth 2008, von Quillfeldt et al. 2009)

10 Conclusions Some highlights from N-ICE2015 Early Phaeocystis blooms under snow-covered sea ice could have far-reaching repercussions on the strength of the biological carbon pump and energy flow through Arctic marine food webs Loss of MYI might compromise seeding of the ice algal spring bloom Pressure ridges play an important but understudied role in Arctic sea ice productivity and might become increasingly important in a more dynamic future icescape Antarctification of the Arctic icescape could lead to more frequent accumulation of phytoplankton at the snow-ice interface The observed changes in ice algal and phytoplankton bloom dynamics will potentially have cascading effects on the entire Arctic food web and may alter the uptake and release of climaterelevant gases from ocean and sea ice.

11 Acknowledgements Mar Fernández-Méndez Hanna Kauko Lasse Mork Olsen 11

12 The biological work package during N-ICE