Meltwater layer dynamics in a central Arctic lead: Effects of lead width, re-freezing, and mixing during late summer
Author:
Nomura Daiki123, Kawaguchi Yusuke4, Webb Alison L.56, Li Yuhong7, Dall’osto Manuel8, Schmidt Katrin9, Droste Elise S.1011, Chamberlain Emelia J.12, Kolabutin Nikolai13, Shimanchuk Egor13, Hoppmann Mario11, Gallagher Michael R.1415, Meyer Hanno16, Mellat Moein16, Bauch Dorothea1718, Gabarró Carolina19, Smith Madison M.2021, Inoue Jun22, Damm Ellen1116, Delille Bruno23
Affiliation:
1. 1Field Science Center for Northern Biosphere, Hokkaido University, Hakodate, Japan 2. 2Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan 3. 3Arctic Research Center, Hokkaido University, Sapporo, Japan 4. 4Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan 5. 5School of Life Sciences, University of Warwick, Coventry, UK 6. 6Department of Chemistry, University of York, York, UK 7. 7Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China 8. 8Institute of Marine Sciences/CSIC, Barcelona, Spain 9. 9School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, UK 10. 10School of Environmental Sciences, University of East Anglia, Norwich, UK 11. 11Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany 12. 12Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA 13. 13Arctic and Antarctic Research Institute, Saint Petersburg, Russia 14. 14Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA 15. 15National Oceanic and Atmospheric Administration, Physical Sciences Laboratory, Boulder, CO, USA 16. 16Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany 17. 17GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany 18. 18Leibniz Laboratory, University of Kiel (CAU), Kiel, Germany 19. 19Barcelona Expert Center (BEC), Institute of Marine Science (ICM-CSIC), Barcelona, Spain 20. 20Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA 21. 21Woods Hole Oceanographic Institution, Woods Hole, MA, USA 22. 22National Institute of Polar Research, Tachikawa, Japan 23. 23Unité d’Océanographie Chimique, Freshwater and Oceanic Science Unit of Research (FOCUS), Université de Liège, Liège, Belgium
Abstract
Leads play an important role in the exchange of heat, gases, vapour, and particles between seawater and the atmosphere in ice-covered polar oceans. In summer, these processes can be modified significantly by the formation of a meltwater layer at the surface, yet we know little about the dynamics of meltwater layer formation and persistence. During the drift campaign of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), we examined how variation in lead width, re-freezing, and mixing events affected the vertical structure of lead waters during late summer in the central Arctic. At the beginning of the 4-week survey period, a meltwater layer occupied the surface 0.8 m of the lead, and temperature and salinity showed strong vertical gradients. Stable oxygen isotopes indicate that the meltwater consisted mainly of sea ice meltwater rather than snow meltwater. During the first half of the survey period (before freezing), the meltwater layer thickness decreased rapidly as lead width increased and stretched the layer horizontally. During the latter half of the survey period (after freezing of the lead surface), stratification weakened and the meltwater layer became thinner before disappearing completely due to surface ice formation and mixing processes. Removal of meltwater during surface ice formation explained about 43% of the reduction in thickness of the meltwater layer. The remaining approximate 57% could be explained by mixing within the water column initiated by disturbance of the lower boundary of the meltwater layer through wind-induced ice floe drift. These results indicate that rapid, dynamic changes to lead water structure can have potentially significant effects on the exchange of physical and biogeochemical components throughout the atmosphere–lead–underlying seawater system.
Publisher
University of California Press
Subject
Atmospheric Science,Geology,Geotechnical Engineering and Engineering Geology,Ecology,Environmental Engineering,Oceanography
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