{"title":"A model for the Arctic mixed layer circulation under a summertime lead: implications for the near-surface temperature maximum formation","authors":"A. Alvarez","doi":"10.5194/tc-17-3343-2023","DOIUrl":null,"url":null,"abstract":"Abstract. Leads in sea ice cover have been studied extensively because of the climatic relevance of the intense ocean–atmosphere heat exchange that occurs\nduring winter. Leads are also preferential locations of heat exchange and melting in early summer, but their oceanography and climate relevance, if\nany, remains largely unexplored during summertime. In particular, the development of a near-surface temperature maximum (NSTM) layer typically\n10–30 m deep under different Arctic basins has been observationally related to the penetration of solar radiation through the leads. These\nobservations reveal that the concatenation of calm and wind events in the leads could facilitate the development of the NSTM layer. Using numerical\nmodeling and an idealized framework, this study investigates the formation of the NSTM layer under a summer lead exposed to a combination of calm\nand moderate wind periods. During the calm period, solar heat accumulates in the upper layers under the lead. Near-surface convection cells are\ngenerated daily, extending from the lead sides to its center. Convection cells affect the heat storage in the mixed layer under the lead and the\nadjacent ice cap. A subsequent wind event (and corresponding ice drift) mixes and spreads fresh and cold meltwater into the warm layers near the\nsurface. Surface mixing results in temperatures in the near-surface layers that are lower than in the deeper layers, where the impact of the surface\nstresses is weaker. Additionally, the warm waters initially located under the lead surface stretch and spread horizontally. Thus, an NSTM layer is\nformed. The study analyzes the sensitivity of the depth and temperature of the NSTM layer to buoyancy forcing, wind intensity, ice drift, stratification,\nand lead geometry. Numerical results suggest that the NSTM layer appears with moderate wind and ice drift and disappears when the wind intensity is\nhigher than 9 m s−1. Depending on the background stratification, the calm period reinforces or becomes critical in NSTM layer\nformation. According to the results, ice drift is key to the development of the NSTM layer.\n","PeriodicalId":56315,"journal":{"name":"Cryosphere","volume":null,"pages":null},"PeriodicalIF":4.4000,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cryosphere","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5194/tc-17-3343-2023","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOGRAPHY, PHYSICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract. Leads in sea ice cover have been studied extensively because of the climatic relevance of the intense ocean–atmosphere heat exchange that occurs
during winter. Leads are also preferential locations of heat exchange and melting in early summer, but their oceanography and climate relevance, if
any, remains largely unexplored during summertime. In particular, the development of a near-surface temperature maximum (NSTM) layer typically
10–30 m deep under different Arctic basins has been observationally related to the penetration of solar radiation through the leads. These
observations reveal that the concatenation of calm and wind events in the leads could facilitate the development of the NSTM layer. Using numerical
modeling and an idealized framework, this study investigates the formation of the NSTM layer under a summer lead exposed to a combination of calm
and moderate wind periods. During the calm period, solar heat accumulates in the upper layers under the lead. Near-surface convection cells are
generated daily, extending from the lead sides to its center. Convection cells affect the heat storage in the mixed layer under the lead and the
adjacent ice cap. A subsequent wind event (and corresponding ice drift) mixes and spreads fresh and cold meltwater into the warm layers near the
surface. Surface mixing results in temperatures in the near-surface layers that are lower than in the deeper layers, where the impact of the surface
stresses is weaker. Additionally, the warm waters initially located under the lead surface stretch and spread horizontally. Thus, an NSTM layer is
formed. The study analyzes the sensitivity of the depth and temperature of the NSTM layer to buoyancy forcing, wind intensity, ice drift, stratification,
and lead geometry. Numerical results suggest that the NSTM layer appears with moderate wind and ice drift and disappears when the wind intensity is
higher than 9 m s−1. Depending on the background stratification, the calm period reinforces or becomes critical in NSTM layer
formation. According to the results, ice drift is key to the development of the NSTM layer.
期刊介绍:
The Cryosphere (TC) is a not-for-profit international scientific journal dedicated to the publication and discussion of research articles, short communications, and review papers on all aspects of frozen water and ground on Earth and on other planetary bodies.
The main subject areas are the following:
ice sheets and glaciers;
planetary ice bodies;
permafrost and seasonally frozen ground;
seasonal snow cover;
sea ice;
river and lake ice;
remote sensing, numerical modelling, in situ and laboratory studies of the above and including studies of the interaction of the cryosphere with the rest of the climate system.