Meltwater layer dynamics in a central Arctic lead: Effects of lead width, re-freezing, and mixing during late summer

peer reviewed 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 th...

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Bibliographic Details
Published in:Elem Sci Anth
Main Authors: Nomura, Daiki, Kawaguchi, Yusuke, Webb, Alison L., Li, Yuhong, Dall'osto, Manuel, Schmidt, Katrin, Droste, Elise S., Chamberlain, Emelia J., Kolabutin, Nikolai, Shimanchuk, Egor, Hoppmann, Mario, Gallagher, Michael R., Meyer, Hanno, Mellat, Moein, Bauch, Dorothea, Gabarró, Carolina, Smith, Madison M., Inoue, Jun, Damm, Ellen, Delille, Bruno
Other Authors: FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège BE
Format: Article in Journal/Newspaper
Language:English
Published: University of California Press 2023
Subjects:
Online Access:https://orbi.uliege.be/handle/2268/312351
https://orbi.uliege.be/bitstream/2268/312351/1/elementa.2022.00102.pdf
https://doi.org/10.1525/elementa.2022.00102
Description
Summary:peer reviewed 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.