Our study highlights unrecognized remarkable ocean warming under the Arctic sea ice over the recent two decades (i.e., the early 21st century) based on the R/V Mirai ※1 shipboard hydrographic dataset.
We suggest that warming of the Pacific-origin water※2 inflowing through the Bering Strait and intensification of the northwestward ocean current along the continental shelf edge both acted to accumulate ocean heat in the downstream region (Figure 1).
Our findings fill an important gap in the understanding of ocean heat distribution/transport, which is a key factor for recent sea ice changes and the habitat shift of potential fishery resources in the central Arctic Ocean.
R/V Mirai
“R/V Mirai” is a research vessel operated by the Japan Agency for Marine–Earth Science and Technology (JAMSTEC). We analyzed the shipboard dataset of seawater temperature and salinity obtained by the 16 Arctic cruises for 1999–2020.
Pacific-origin water
“Pacific-origin water” is a water mass inflowing from the North Pacific to the Arctic Ocean through the Bering Strait. This seawater has higher salinity and density than the cold riverine water widely covering the Arctic sea surface. Therefore, the Pacific-origin water intrudes into the subsurface layer under the sea ice and riverine water in spite of its warmer temperature.
Figure 1. Schematic image of a role of the Pacific-origin water in floor heating under the Arctic sea ice
Dr. Eiji Watanabe at the Japan Agency for Marine–Earth Science and Technology (JAMSTEC; President, Hiroyuki Yamato) detected remarkable subsurface warming around the Chukchi Borderland in the Arctic Ocean over the recent two decades (i.e., the early 21st century), in collaboration with Dr. Hiromichi Ueno at Hokkaido University and Dr. Kohei Mizobata at Tokyo University of Marine Science and Technology. Whereas sea ice decline in the Arctic Ocean is recognized as a serious issue of global environmental changes, the record minimum of the Arctic sea ice extent has not been updated since 2012. Previous studies reported continuous ocean warming under the sea ice cover in the Canadian side of the Arctic Ocean and indicated the enhanced inflow of the Pacific-origin warm water as a primary factor. Since this ocean heat has a potential to cause the drastic decline of overlying sea ice, it is highly important to understand spatial and temporal variability in the ocean heat distribution associated with the Pacific-origin water transport. Here we found the unrecognized remarkable accumulation of ocean heat around the Chukchi Borderland, located northwest of Alaska, by the synthetic analysis of hydrographic (temperature and salinity) data obtained by the R/V Mirai cruise for 1999–2000 (Figure 2). We then suggested that warming of the Pacific-origin water inflowing through the Bering Strait and intensification of the northwestward ocean current along the shelf–basin boundary from Barrow Canyon both could account for accumulation of ocean heat in the downstream region. Our findings fill an important gap in the understanding of ocean heat distribution/transport, which is a key factor for recent sea ice changes and the habitat shift of potential fishery resources in the central Arctic Ocean.
Figure 2. Subsurface ocean heat content in the southern Chukchi Borderland region [MJ/m2]. (Left) Spatial distribution at all stations analyzed in our study. (Right) Interannual time series for 1999–2020. Black dots show the subsurface ocean heat content calculated using the mooring-based dataset in Barrow Canyon.
These findings were published in Scientific Reports on January 10. This work was supported by the Arctic Challenge for Sustainability (ArCS II: JPMXD1420318865) and the Grant-in-Aid for Scientific Research of Japan Society for the Promotion of Science (JSPS: 22221003, 15H01736, and 18H03368).
Miaki Muramatsu1,2*, Eiji Watanabe1*, Motoyo Itoh1, Jonaotaro Onodera1, Kohei Mizobata1, and Hiromichi Ueno2
For this study
Senior Researcher Eiji Watanabe
Research Institute for Global Change(RIGC)
Institute of Arctic Climate and Environment Research(IACE)
Arctic Ocean Environment Research Group, JAMSTEC
Professor Hiromichi Ueno
Department of Marine Environmental Science
Faculty of Fisheries Sciences
Hokkaido University
Associate Professor Kohei Mizobata
Tokyo University of Marine Science and Technology
Department of Ocean Sciences
For press release