PNW Ocean Hypoxia Zones Usually Arrive In June Or July; This Year, They Came In April
Nearly two decades ago, fishers discovered an odd occurrence off the coast of Oregon. They were pulling up pots of dead or lethargic crabs. At first they suspected a chemical spill or a red tide. But instead, they learned, dangerously low levels of dissolved oxygen in the ocean water were to blame. The crabs had suffocated. These swaths of hypoxic areas have surfaced every summer on Pacific Northwest shores since it was first recorded in 2002. They are spurred by naturally occurring coastal upwellings and algae blooms, exacerbated by climate change, said Francis Chan, director of the Cooperative Institute for Marine Resources Studies at Oregon State University.
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Typically, hypoxic conditions havent arrived to the nearshore until mid-June or July. This year hypoxic conditions were reported in April with the upwelling season beginning in March. To get a sense of why an early beginning to the upwelling season is concerning, Chan compared it to the summer drought season. Say we expected rainfall lasting until March but the rain stops in February. Thats all the water we have. We have to last until next year.
Similarly, if upwelling starts a month earlier than usual, the amount of oxygen, already low, has to last until the fall when storms promote mixing which adds oxygen back into the system. Chan said as of late September this year, upwelling is still occurring and low levels of oxygen are still persisting.
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On a global scale, the oceans are already losing oxygen. Take this and add local factors like coastal upwelling and phytoplankton bloom decomposition off Washington and Oregon coasts, and you have a system with severely low oxygen levels. While upwelling ecosystems like the CCLME were once thought as resilient in the face of climate change because of their dynamic nature, they have quickly and quietly become places scientists say will be hit hard by changing conditions.
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https://www.seattletimes.com/seattle-news/low-oxygen-levels-along-pacific-northwest-coast-a-silent-climate-change-crisis/