Vertical feedback mechanism of winter Arctic amplification and its relative role to horizontal process
학위논문(박사)--서울대학교 대학원 :자연과학대학 지구환경과학부,2019. 8. Kim, Kwang-Yul. Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of Arctic sea ice, which remains to be controversial. In the present study, detailed physical mechanism of sea...
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| Other Authors: | , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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서울대학교 대학원
2019
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10371/162432 http://dcollection.snu.ac.kr/common/orgView/000000156585 |
| Summary: | 학위논문(박사)--서울대학교 대학원 :자연과학대학 지구환경과학부,2019. 8. Kim, Kwang-Yul. Sea ice reduction is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of Arctic sea ice, which remains to be controversial. In the present study, detailed physical mechanism of sea ice reduction in winter (December–February) is identified from the daily ERA interim reanalysis data. Downward longwave radiation is an essential element for sea ice reduction, but can primarily be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. The increased turbulent heat flux is used to increase air temperature and specific humidity in the lower troposphere, which in turn increases downward longwave radiation. This feedback process is clearly observed in the Barents and Kara Seas in the reanalysis data. A quantitative assessment reveals that this feedback process is being amplified at the rate of ~8.9% every year during 1979–2018. Availability of excessive heat flux is necessary for the maintenance of this feedback process; a similar mechanism of sea ice loss is expected to take place over the sea-ice covered polar region, when sea ice is not fully recovered in winter. Moreover, relative role of vertical processes resulting from the reduction of sea ice in the Barents-Kara Seas is not clearly understood in comparison with the horizontal heat and moisture advection. Moisture, thermal energy and moist static energy budgets are analyzed over the region of sea ice reduction in order to delineate the relative roles of horizontal and vertical processes. A detailed analysis of energy and moisture budgets in the atmospheric column indicates that both the vertical source from the release of heat flux and moisture due to sea ice reduction and the horizontal advection of heat and moisture are essential for explaining the variation of temperature and specific humidity over the Barents-Kara Seas. The vertical flux term explains a slightly larger fraction of the mean ... |
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