Ocean heat transport on the Pacific side of the Arctic Ocean has increased 1.5 times over the past 20 years
~ Increased warm water inflow would play a key role in the sea ice decline ~
1. Key Points
- A mooring observation※1 conducted by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) from 2000 to 2022 revealed that ocean heat transport by warm water flowing into the Canada Basin※2 on the Pacific side of the Arctic Ocean has increased by approximately 1.5 times over the past two decades.
- In the Chukchi Sea, which is upstream of the Canada Basin, summer sea ice extent has been decreasing due to long-term warming of Pacific-origin water※3 through the Bering Strait. A feedback loop is accelerating sea ice loss and ocean surface warming through the increased absorption of solar radiation during the summer. As a result, ocean heat transport into the Canada Basin has largely increased due to further warming of Pacific-origin water (Figure 1).
- The increased ocean heat transport of Pacific-origin water accumulates in the Canada Basin where it is positioned to act as a year-round source of heat to the sea ice potentially causing further sea‑ice melting and associated environmental changes. It is important to continue monitoring these changes that also affect the marine organisms living in the region.
Mooring observations
An observational method in which instruments for measuring water temperature, current, and other oceanographic variables are deployed in the ocean. A mooring system is installed from a research vessel and recovered one to two years later, allowing continuous data collection throughout the year - including winter, when research vessels have difficult to access the Arctic Ocean. The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is a unique institute which has conducted the long-term mooring observations capturing decadal changes in the warm water flowing into the Canada Basin.
Basin
A deep‑sea region with its seafloor depth of approximately 3,000 meters.
Pacific-origin water
A water mass that flows from the North Pacific into the Arctic Ocean through the Bering Strait. This seawater is warm in summer, and cold and nutrient‑rich in winter.
Figure 1. Schematic overview of the mechanism driving the increase in ocean heat transport into the Canada Basin
2. Abstract
Dr. Motoyo Itoh at the Japan Agency for Marine–Earth Science and Technology (JAMSTEC; President, Hiroyuki Yamato) revealed that ocean heat transport of the Pacific-origin water into the Canada Basin on the Pacific side of the Arctic Ocean has increased 1.5 times over the recent two decades, under the collaboration with the Institute of Ocean Sciences, Fisheries and Oceans Canada.
Since the 1990s, Arctic sea ice has been declining due to global warming, and the reduction in summer sea‑ice extent on the Pacific side of the Arctic Ocean, including the Chukchi Sea and the Canada Basin, has been particularly pronounced. Warm Pacific‑origin water, which plays a key role in sea‑ice reduction and ocean warming on the Pacific side of the Arctic Ocean, flows off Point Barrow (Barrow Canyon) into the Canada Basin. JAMSTEC has been conducting mooring observations in Barrow Canyon, deploying instruments that measure ocean temperature and current in the water, from 2000 to the present.
In this study, we revealed that the ocean heat transport of Pacific‑origin water flowing through Barrow Canyon into the Canada Basin has increased 1.5 times over the past 20 year, based on our mooring observation (Figure 2). In addition, an analysis covering approximately 40 years (1982–2022), incorporating satellite observations, revealed that this ocean heat transport began to increase rapidly in the late 2010s. We found that the increase in ocean heat transport is attributable not only to the warming of the upstream Bering Strait but also to a feedback process in the Chukchi Sea, where the reduction in sea ice allows surface water to absorb more solar radiation as it flows northward (Figure 1). This absorption raises the water temperature, further enhances sea‑ice melt, and leads to a long‑term increase in the temperature of Pacific‑origin water entering the Canada Basin. The warm Pacific‑origin water that flows into the Canada Basin melts sea ice in summer and delays freeze‑up in winter, thereby reducing sea‑ice amount and increasing the temperature of the water below the sea ice. Because sea‑ice reduction and ocean warming trigger comprehensive environmental changes, including impacts on the marine organisms living in the region, it is important to continue long‑term observations.
These findings were published in Journal of Geophysical Research Oceans on February 13. This work was supported by the Arctic Challenge for Sustainability project Phase II (ArCS II: JPMXD1420318865) and III (ArCS III: JPMXD1720251001), the Grant-in-Aid for Scientific Research of Japan Society for the Promotion of Science (JSPS: 22221003, 15H01736, and 18H03368), the Fisheries and Oceans Canada and others.
Figure 2. Ocean heat transport (red line), sea surface temperature (blue line), and sea‑ice concentration (green line) in Barrow Canyon. The ocean heat transport is derived from mooring observations, while the sea surface temperature and sea‑ice concentration (the proportion of the area covered by sea ice) are obtained from satellite.
Motoyo Itoh1, Shigeto Nishino1, Takashi Kikuchi1, Humfrey Melling2, Sarah Zimmermann2, William J. Williams2, Eddy C. Carmack2
- Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.
- Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, British Columbia, Canada
For this study
For press release