2022 Fiscal Year Research-status Report
Sea ice melt and its impact on the upper ocean properties in a warming Pacific Arctic
| Project/Area Number |
22K14094
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| Research Institution | Hokkaido University |
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Principal Investigator |
MENSAH VIGAN 北海道大学, 低温科学研究所, 特任助教 (10912678)
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| Project Period (FY) |
2022-04-01 – 2024-03-31
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| Keywords | Sea Ice melt / Pacific Arctic / Global warming / Ocean observations / Remote sensing / Multi-Decadal trend |
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| Outline of Annual Research Achievements |
We successfully tested and implemented a methodology for estimating sea ice melt amount from ocean observations in the Bering Sea. Total freshwater thickness was first estimated from temperature and salinity data, and the effects of river waters were then removed using oxygen isotope ratio data.
Validation using satellite-derived estimates of sea ice production and thickness revealed good consistency. Further data analysis revealed a significant decrease in the Bering Sea ice production/melt starting before 1980.
We then estimated precisely the sea ice melt volume in the Chukchi and Beaufort seas, and detected an increasing trend in sea ice melt volume after 2005. This trend is related to the melting of multi-year ice over the past 2 decades, and has not been quantified before.
We organised an international workhshop in October 2022 to introduce the project, gather knowledge and discuss research collaboration and data exchange. The workshop gathered 27 participants, including 4 partipants from foreign institution (following this, a research collaboration between a professor of National Central University in Taiwan and 2 Japanese scientists at Hokkaido University and Tokyo University was established).
We further presented results of our research at the 7th International Symposium on Arctic Research, held by the National Institute of Polar Science. Through this meeting, two more research collaborators are likely to join the project
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Estimating sea ice melt in the Arctic Ocean is challenging due to the presence of river waters, whose signal is merged with that of sea ice melt. We were not sure whether we would be able to separate the contribution of river waters during FY2022. However, this was achieved, and thanks to this we could obtain reliable estimates of melt water amount in the Beaufort Sea, a hotspot for changes related to global warming.
The positive trend in sea ice melt we found in the Beaufort Sea (related to the melting of multi-year ice) is clear and consistent with the ocean circulation and Ice drift in the Beaufort Sea. This is a major result that we did not expect to obtain in such a clear way.
Discussions with domestic and international scientists were fruitful and allowed to expand the number of research collaborators.
Ms. Y-C Chen, a research collaborator from National Central University (Taiwan), visited Hokkaido University twice and participated in the development of the ice melt estimation methodology. She also took significant role in the processing of data in the Beaufort and Chukchi Sea. Her contribution has been very valuable.
D. Nomura (Hokkaido University) recently joined the project and provided additional data in the Bering Sea. M. Kawai (Tokyo University of Marine Science and Technology, "Tokyo Kaiyodai" hereafter) is likely to join the project and provide her expertise about oxygen isotope analysis as well as additional data in the Beaufort Sea.
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| Strategy for Future Research Activity |
We plan to write and submit two separate scientific publications. The first paper (Bering Sea) will introduce and delineate our methodology, climatology of sea ice melt, as well as time series and climatologies before/after 1990 to highlight the decadal changes in ice production and melt. Before this, we will adjust the methodology to better estimate ice melt in years with extremely low sea ice production (2016-2020).
The second paper will focus on the Beaufort Sea and introduce the estimates of ice melt and increasing trend in this sea. Prior to that, we hope to gather additional oxygen isotope data to refine our river water estimates. This will be made easier if M. Kawai from Tokyo Kaiyodai joins the project. This second paper may be submitted in early FY2024.
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| Causes of Carryover |
One of the guest for Kakenhi-funded "The International Workshop on Pacific Arctic Sea ice Melting 2022" (M. Itoh, JAMSTEC) attended the meeting online rather than on-site in Hokkaido University, thus no travel expense were incurred from her participation.
The usage plan for next fiscal year will be to purchase a perpetual license of the data analysis softward MATLAB.
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