Ocean Characteristics Near the Galapagos
The Galapagos Islands are situated in the Pacific Ocean in tropical waters near the Equator. The waters around the islands are characterized by upwelling, where cooler water from the depths is brought near the surface. Upwelling causes the waters around the Galapagos to be nutrient-rich. The euphotic zone (the surface area in the ocean that is about 100m deep and contains the bulk of biological productivity) is particularly rich in nitrates (Rapaport 1999).
This upwelling is caused in particular by two currents: the South Equatorial Current, which flows westward, and the cold Cromwell current (AKA the Equatorial Undercurrent) which flows eastward. Other ocean currents also affect the Galapagos Islands: the cold Peru Coastal or Humboldt Current and the Peru Oceanic from the south, and the warm Nino or Panama Current from the North. There are also inter-island currents. Those affecting our area consist of a southerly-flowing current running from the Wolf Islands to Santiago and an easterly-flowing current running from Isabela to Santa Cruz (Rapaport 1999).
Normal sea surface temperatures around the Galapagos Islands range from 18-23 degrees Celsius. These temperatures vary among the islands. Five different climate zones have been described around the archipelago. Most of our islands fall into the central zone, Zone 1, with Santiago being in Zone 4. These two zones have median SSTs in the archipelago (Grove & Lavenberg 1997).However, these temperatures increase in the case of an El Nino. In 1997, the average temperatures went up five degrees (Rapaport 1999).
El Nino has a large effect on the Galapagos Islands. This abnormally warm current has fewer nutrients and a lower salinity, having an impact on the marine species. El Ninos occur once in a two to seven year period, but have been increasing in intensity over the past few decades. They increase the rainfall, aiding terrestrial wildlife, but negatively impact marine life (Rapaport 1999).
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