Arctic ice melt changing major ocean current

White blobs on a flat dark shiny background - patches of melting ice on water.
Image via NASA/ Kathryn Hansen.

New research suggests that a major ocean current in the Arctic is faster and more turbulent as a result of rapid sea ice melt, an effect of human-caused climate change. The current, called the Beaufort Gyre, has seen an influx of unprecedented amounts of cold, fresh water. It’s a change, say the researchers, that could alter the currents in the Atlantic Ocean and cool the climate of Western Europe.

The Beaufort Gyre is a wind-driven ocean current located in the Arctic Ocean polar region. The gyre contains both ice and water. It accumulates fresh water by the process of melting the ice floating on the surface of the water. The study, published February 6, 2020, in the peer-reviewed journal Nature Communications, used 12 years of satellite data to analyze how this circular current has been affected by the increase in fresh water from increased ice melting.

Map of Arctic Ocean and North Atlantic Ocean showing currents including circular current around North Pole.
Arctic ocean circulation. Image via NSIDC.

The researchers explained:

The Beaufort Gyre keeps the Arctic polar environment in equilibrium by storing fresh water near the surface of the ocean. Wind blows the gyre in a clockwise direction around the western Arctic Ocean, north of Canada and Alaska, where it collects fresh water from glacial melt, river runoff and precipitation. This fresh water is important in the Arctic in part because it floats above the warmer, salty water and helps to protect the sea ice from melting, which in turn helps regulate Earth’s climate. The gyre then slowly releases this fresh water into the Atlantic Ocean over a period of decades, allowing the Atlantic Ocean currents to carry it away in small amounts.

But the since the 1990s, the gyre has accumulated a large amount of fresh water – 1,920 cubic miles (8,000 cubic km) – or almost twice the volume of Lake Michigan. The new study found that the cause of this gain in freshwater concentration is the loss of sea ice in summer and autumn. This decades-long decline of the Arctic’s summertime sea ice cover has left the Beaufort Gyre more exposed to the wind, which spins the gyre faster and traps the fresh water in its current.

In addition, persistent westerly winds have dragged the current in one direction for over 20 years, increasing the speed and size of the clockwise current and preventing the fresh water from leaving the Arctic Ocean. This decades-long western wind is unusual for the region, said the researcher. Previously, the winds changed direction every five to seven years.

NASA/JPL polar scientist Tom Armitage is the study lead author. He said in a statement:

If the Beaufort Gyre were to release the excess fresh water into the Atlantic Ocean, it could potentially slow down its circulation. And that would have hemisphere-wide implications for the climate, especially in Western Europe.

Fresh water released from the Arctic Ocean to the North Atlantic can change the density of surface waters. Normally, water from the Arctic loses heat and moisture to the atmosphere and sinks to the bottom of the ocean, where it drives water from the north Atlantic Ocean down to the tropics like a conveyor belt. This current, called the Atlantic Meridional Overturning Circulation, helps regulate the planet’s climate by carrying heat from the tropically-warmed water to northern latitudes such as Europe and North America. If slowed enough, the researchers said, it could affect marine life, as well as the communities that depend on it.

Bottom line: New research says the Beaufort Gyre, a major ocean current in the Arctic, is faster and more turbulent as a result of rapid sea ice melt.

Source: Enhanced eddy activity in the Beaufort Gyre in response to sea ice loss

Read more about the study from NASA/JPL

February 21, 2020

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