Beaufort Gyre

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Transpolar Drift and Beaufort Gyre are major ocean currents within the Arctic Ocean.

The Beaufort Gyre is one of the two major ocean currents in the Arctic Ocean. It is roughly located north of the Alaskan and Canadian coast. In the past, Arctic sea-ice would circulate in the Beaufort gyre up to several years, leading to the formation of very thick multi-year sea-ice.[1] Due to warming temperatures in the Arctic, the gyre has lost an extensive amount of ice, practically turning what used to be a nursery for sea-ice to mature and grow into the thickest and oldest ice of the Arctic Ocean into a "graveyard" for older ice.[2][3]

Dynamical mechanisms

Conditions in the Arctic have favored sea ice loss in recent years during the Northern Hemisphere summers. At the end of the 20th century, analyses of increasing Pacific Surface Water temperatures led to the discovery of a connection between these rising temperatures and the onset of severe loss of Arctic sea ice in the Beaufort Sea. A reason for the existence of this link was proposed: "...delayed winter ice formation allows for more efficient coupling between the ocean and wind forcing." These dynamical mechanisms are observed in the spin-up and circulation of the Beaufort Gyre.[4]

Arctic Sea Ice Age: 1984 - 2019

Housed in the western part of the

submarines, ships, and stations on drifting ice suggest that the gyre has been expanding over the past two decades. Researchers have employed coupled sea-ice-ocean general circulation models in order to thoroughly analyze these observations. Model results show that Ekman transport
plays an integral role in the variability of freshwater in the gyre, and thus in the Arctic Ocean. The prevailing rotational direction of the Beaufort Gyre is clockwise, following the prevailing wind circulation of the Polar High. Coriolis veers moving objects to the right in the northern hemisphere and "to the right" is inwards in a clockwise rotating system. This is why anything floating, including fresher water, tends to move toward the centre of the system. Indeed, there is a slight bulge in the centre of the Beaufort gyre when it is rotating in its predominant clockwise direction. If, as is speculated, as the Arctic Ocean becomes a heat collector resulting in a low pressure, counter clockwise rotating system, the Beaufort Gyre can be expected to follow suit and send the fresher water outward to be captured by the transpolar current. This could well bring up the saltier, slightly warmer Atlantic water which lies under the floating, fresher Arctic water.

Variations in the Ekman transport change the sea surface height and depth of the halocline, resulting in Ekman pumping. During anticyclonic regimes—where the wind stress curl is negative—freshwater is pumped into the Beaufort Gyre; during cyclonic regimes—where wind stress curl is positive—freshwater is released into the Arctic Ocean, where it can then flow into the North Atlantic. Giles et al. (2012)[5] conclude that the variability in freshwater content varies with wind stress curl. The wind stress curl used by Giles et al. (2012) is from the NCEP/NCAR Reanalysis data at the National Oceanic & Atmospheric Administration, Earth System Research Laboratory, Physical Sciences Division (NOAA/OAR/ESRL PSD) in Boulder, Colorado, USA.

The seasonal cycle of freshwater content does not only concern mechanical (Ekman pumping) processes, but thermal (ice formation) processes as well. The Beaufort Gyre contains a mean volume of 800 km3 of frozen freshwater, or sea ice, based on a mean ice thickness of 2 meters. During the June–July months, the mean seasonal cycle of freshwater content peaks; in this season, sea ice thickness reaches a minimum, implying that the amount of melted sea ice has reached a maximum. The maximum in freshwater content released into the ocean waters coincides with a maximum in wind stress curl (i.e., a minimum in Ekman pumping), allowing for a high volume of freshwater to seep into the Arctic Ocean circulation. This rapid influx of freshwater into the Arctic circulation forces a large volume of freshwater to outflow into the

Atlantic Meridional Overturning Circulation.[6]

Studies

The Beaufort Gyre has formed a dome of

Atlantic
ocean would occur.

Thermohaline Circulation and thus climate.[8]

Due to seasonal sea ice formation, the Beaufort Gyre is difficult to access and thus study in the Northern Hemisphere winter months; the lack of sunlight in these months forces the use of artificial light.[9] Studies by Arthur S. Dyke and others show that if the volume of outflow of rivers into the Beaufort Gyre increase, the gyre itself might spatially shift toward the right.[10]

See also

References

  1. ^ "Dynamics: Circulation | National Snow and Ice Data Center". nsidc.org. Retrieved 2020-09-07.
  2. ^ "Arctic Sea Ice Age 2016". svs.gsfc.nasa.gov. Retrieved 2020-09-07.
  3. ^ "2019 Arctic Report Card: Old, thick ice barely survives in today's Arctic | NOAA Climate.gov". www.climate.gov. Retrieved 2020-09-07.
  4. S2CID 1645303
    .
  5. doi:10.1038/ngeo1379
    .
  6. hdl:1912/3680
    .
  7. ^ a b Amos, Jonathan (23 January 2012). "Arctic Ocean freshwater bulge detected". BBC News. Retrieved 23 January 2012.
  8. ^ "On top of the World". Oceanus. FindArticles. September 2005. Archived from the original on 2012-07-08. Retrieved 19 October 2009.
  9. ^ Lippsett, Lonny (2005), "The Flywheel of the Arctic Climate Engine: Remote Beaufort Gyre Expeditions Reveal Clues to Climate Change", Oceanus, 44 (3): 28. Expanded Academic ASAP. Web. 13 Oct. 2009.
  10. doi:10.14430/arctic1086
    . Expanded Academic ASAP. Web. 13 Oct. 2009.

External links
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