JAMSTEC reveals that ocean heat transport to the Pacific side of the Arctic Ocean increased 1.5 times over 20 years

Researcher Motoyo Itoh with the Arctic Ocean Environment Research Group, Institute of Arctic Climate and Environment Research (IACE), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), working in collaboration with the Institute of Ocean Sciences, Fisheries and Oceans Canada, announced that ocean heat transport by Pacific-origin water flowing into the Canada Basin on the Pacific side of the Arctic Ocean has increased 1.5 times over approximately two decades. Mooring observations have been ongoing since 2000, and combined analysis using satellites and other data also revealed that this increase is driven not only by warming of upstream water but also by a feedback process in which sea surface exposed by sea ice decline absorbs more solar radiation. The findings are expected to contribute to climate change countermeasures. The results were published in the Journal of Geophysical Research: Oceans on February 13.

In the Arctic region, the summer sea ice extent has been declining due to global warming, falling to 50-70% of 1979-1999 levels since 2010. In the Pacific sector of the Arctic Ocean in particular, the period during which sea ice melts completely has increased by more than 30 days over the past 30 years. This sea ice decline is thought to be caused by warm Pacific-origin water flowing through the Bering Strait into the Pacific side of the Arctic Ocean.

However, the long-term changes in ocean heat transport by Pacific-origin water flowing into the Canada Basin, which sits at the Pacific entrance to the Arctic Ocean, had not been well understood.

To track changes in warm water flowing into the Canada Basin, JAMSTEC has maintained three mooring systems in Barrow Canyon, which lies at the entrance to the basin, to continuously conduct monitoring since 2000. The mooring systems are used as an observation means in which a rope fitted with instruments such as thermometers and current meters is anchored to the seafloor to record various data. The systems are recovered and replaced every one to two years, enabling continuous monitoring of data variations.

Pacific-origin water flows from the Bering Sea through the Bering Strait into the Chukchi Sea, which is part of the Arctic Ocean. It was already known that in summer approximately 90% of this water passes through Barrow Canyon and spreads further downstream into the Canada Basin.

Analysis of the accumulated mooring data revealed a long-term rising trend in water temperature, accompanied by an increasing trend in ocean heat transport (0.068 TW/year), amounting to a 1.5-fold increase over approximately 20 years. Analysis of seasonal variations further showed that an increase in the heat content (i.e., a temperature rise) of Pacific-origin water from summer to autumn accounts for this trend.

Meanwhile, although an increasing trend was found in heat transport through the upstream Bering Strait, this did not correspond to the year-to-year variability observed at Barrow Canyon.

The researchers therefore examined the possibility that changes in Pacific-origin water within the Chukchi Sea were having a strong influence. They investigated the ocean heat transport at Barrow Canyon and satellite-derived variations in the sea ice (concentration) and sea surface temperature in Chukchi Sea.

The results showed a strong correlation among all three variables. It was found that heat transport variability at Barrow Canyon is strongly influenced by the sea ice extent in the northeastern Chukchi Sea during early summer. Heat transport was greater when sea ice was less extensive and water temperatures were higher, and less when sea ice was more extensive and temperatures were lower.

When sea ice is present, most of the incoming solar radiation is reflected. However, as rising water temperatures cause sea ice in the Chukchi Sea to melt and open ocean areas expand, the ocean is thought to absorb a much greater portion of the solar heat.

Itoh commented: "Increasing ocean heat transport is triggering a range of complex environmental changes in the Canada Basin, including ocean warming and sea ice decline. Because these changes also affect the organisms that live in the region, it is important to continue such observations going forward."

Journal Information
Publication: Journal of Geophysical Research Oceans
Title: Increased Heat Transport Through Barrow Canyon and Its Impact on Subsurface Warming in the Western Arctic Ocean
DOI: 10.1029/2025JC022717