Upwelling is an oceanic process whereby cold, nutrient rich deep water is brought to the surface by various oceanographic or geographic mechanisms, over a period of time. One driver of upwelling are the winds blowing across the ocean’s surface, parallel to the coast and displace the warmer, nutrient poor surface waters, allowing the colder, deeper water to rise to the surface, carrying nutrients with it. The deeper ocean water is nutrient rich due to the decomposition of marine animals which have sunk to the deeper ocean waters. Upwelling is an extremely dynamic process ,influenced by factors such as the direction and strength of winds and coastline topography.
Regions of upwelling are important because they bring nutrients up from the ocean floor to provide food for phytoplankton and eventually fish stocks in an otherwise nutrient depleted euphotic zone. Upwelling also aids in the dispersion of marine lava to areas in which they may not survive, so therefore has a detrimental effect on marine stock.
Some of the most productive fishing grounds in the world occur off the coast of South America, in Peru, Equador and northern Chile. Upwelling here brings nutrient rich waters to support a vast quantity of phytoplankton which in turn provides plentiful food for fish and other marine animals. However, during an El Niño event, (a periodic fluctuation in sea surface temperature which occurs roughly every seven years) less dense, warm, nutrient-poor water is transported from the equator by the Peru Countercurrent. This causes the upper, nutrient poor oceanic layers to deepen, so that the upwelled waters are alo nutrient poor. In addition, the coastal wind system can diminish during an El Niño event, causing upwelling to virtually cease altogether. These events can last for as long as 12 to 18 months and cause a decline in fish productivity and starvation amongst marine animals. Climate change could increase upwelling in this area due to increased wind stress and research has found that coastal wind stress has been increasing over the last 40 years..
Works Cited
Anonymous. “Global warming to increase ocean upwelling, but fisheries impact uncertain.” Life Science Weekly (2015): 635.
Bakun, A. “Global Climate Change and Intensification of Coastall Ocean Upwelling.” Science 247.4939 (1990): 198.
Clayton, M.N. and King, R.J. Biology of Marine Plants. Melbourne: Longman Cheshire Pty. Limited, 1990.
NASA. Wind Driven Surface Currents: Upwelling and DownWelling. n.d. <http://oceanmotion.org/html/background/upwelling-and-downwelling.htm>.
NOAA . What is Upwelling? 9 February 2015. <http://oceanservice.noaa.gov/facts/upwelling.html>.
