Graphic Images of the Haida Eddy

Prepared by Bill Crawford and Frank Whitney

Sea surface height maps showing the Haida and Sitka Eddies

The images in the zip file below show sea surface elevations as measured by TOPEX/Poseidon and ERS-2 satellite altimeters. Red regions denote high sea surface and blue regions denote depressions. Eddies appear as red. The original data were processed by the Colorado Center for Astrodynamics Research, and we have added labels to show the drift of Haida and Sitka eddies between February 1998 and September 2005.

Sea Surface Height Maps 1998-2005 .zip file.

Transport of nutrients from an anticyclonic eddy to surrounding waters.

Transport of nutrients from an anticyclonic eddy to surrounding waters.

A result of mixing between an eddy and surrounding waters is the production of nutrient-rich waters which enhance transport of nutrients to the euphotic zone. In September, 1998, we observed 2 to 3 times the biomass at the base of the euphotic zone on the edges of Haida-1998.

Light transmission through Haida-1998

Donut effect of feeding in eddies in the Gulf of Alaska

Donut effect of feeding in eddies in the Gulf of Alaska

Plankton are small plants and animals that support most of the life in the ocean, including fish, seabirds and marine mammals such as dolphins and whales. We count their numbers by measuring how well they block the path of a short beam of light sent out by a transmissometer lowered from our research vessels. Anywhere away from the coast, plankton abundance is low in a typical September in the Gulf of Alaska.

Frank Whitney lowered a transmissometer through Haida-1998 in September 1998. A graph of these measurements above shows low transmission (and more plankton) between 40 and 60 metres below the ocean surface, but only in the outer rings of the eddy at 50 to 100 kilometres away from the core. He found less plankton in the centre of this eddy and in the surrounding ocean. If we could look at this plankton-rich region from above, it would have the shape of a donut.

What's going on?

Most of this ocean in September has too little light, or too few nutrients to allow plankton to grow. Within 30 to 40 metres of the surface where light levels are high, plankton use up the nutrients during the spring. In the eddy core, the spinning motion of the eddy itself pushes nutrient-rich waters, which came from the coast of North America, down to depths where little light penetrates. But outside the core of this eddy at depths between 40 and 60 metres, both light levels and nutrients that are shed from the eddy core are plentiful enough to support 2 to 3 times more plankton than normal.

Other Graphics

  • Sea surface height map showing ocean elevations along the west coast of Canada during the winter of 1998.
  • Cross section of temperature and salinity through Haida-1998 in September 1998, as measured by Frank Whitney on the Canadian Coast Guard Vessel J.P. Tully.

Publications

Research papers on Haida Eddies are published in a special issue of Deep-Sea Research Part II in 2005. Titles of these papers are listed below:

Date modified: