page_title: Haida Eddies
section_title: Historical observations
hierarchical_section_title: Haida Eddies / Historical observations
caption_attribution_description: English: Ocean color from the SeaWIFS satellite, showing an anticyclonic Haida Eddy in the Alaska Current on June 13, 2002
context_page_description: Haida Eddies are episodic, clockwise rotating ocean eddies that form during the winter off the west coast of British Columbia’s Haida Gwaii and Alaska’s Alexander Archipelago. These eddies are notable for their large size, persistence, and frequent recurrence. Rivers flowing off the North American continent supply the continental shelf in the Hecate Strait with warmer, fresher, and nutrient-enriched water. Haida eddies are formed every winter when this rapid outflow of water through the strait wraps around Cape St. James at the southern tip of Haida Gwaii, and meets with the cooler waters of the Alaska Current. This forms a series of plumes which can merge into large eddies that are shed into the northeast Pacific Ocean by late winter, and may persist for up to two years.
  Haida eddies can be more than 250 km in diameter, and transport a mass of coastal water approximately the volume of Lake Michigan over 1,000 km offshore into the lower nutrient waters of the northeast Pacific Ocean. These "warm-core rings" transport heat out to sea, supplying nutrients to nutrient depleted areas of lower productivity.
context_section_description: Due to their large size, it was not until the satellite era that scientists were able to observe the full scale and life cycles of Haida eddies. Their extent is such that an ocean liner can move through the eddy without observing its borders, so accurate records did not exist until the late 1980s.
  Between 1985-1990, the first US research mission to study changes in sea surface height using radar altimetry (an instrument used to measure the ocean surface height using a radar pulse in reference to a geoid), was conducted by the US Navy using the Geodetic/Geophysical Satellite (GEOSAT). The primary focus was to study fronts, eddies, winds, waves, and tides; each of these processes produce a change in sea surface height of several meters. In 1986, researchers Gower and Tabata observed clockwise eddies in the Gulf of Alaska using GEOSAT - the first satellite observation of Haida eddies. In 1987, the Ocean Storms program deployed 50 drifters to examine intertidal oscillations and mixing during fall storms and observed eddies propagating westward. Also in 1987, researchers Richard Thomson, Paul LeBlond, and William Emery observed that ocean drifters deployed in the Gulf of Alaska at 100–120 meters below the surface had stopped their eastward motion and actually began to move westward counter to the predominant current. The researchers attributed the unexpected motion to eddies dragging the buoys westward from their path at approximately 1.5 cm/s.
  In 1992, Haida eddies were observed by researchers Meyers and Basu as positive sea surface height anomalies using TOPEX-POSEIDON, an altimetry-based satellite platform (like GEOSAT). They specifically noted an increase in the number of Haida eddies during the 1997/1998 El Niño winter. Haida eddy altimetry observations were further supplemented by European Remote Sensing satellites, ERS1 and ERS2. In 1995 Richard Thomson, together with James Gower at the Institute of Ocean Sciences in British Columbia, discovered the first clear evidence of eddies along the entire continental margin using temperature maps from infrared observations using National Oceanic and Atmospheric Administration (NOAA) satellites. Satellite observations coupled with drifter observations have allowed scientists to resolve physical and biogeochemical structures of Haida eddies.
caption: NASA Visible Earth image; ocean color from the SeaWIFS satellite, showing an anticyclonic Haida eddy in the Alaskan Current, southwest of Haida Gwaii.
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