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Map showing a marine heat wave known as “the blob” which spread across the northeastern Pacific Ocean from 2014 to 2016. Image: Joshua Stevens/NASA Earth Observatory, Data: Coral Reef Watch

Modeling “the blob” in the Salish Sea

In late 2013, a marine heatwave that scientists dubbed “the blob” began warming the ocean throughout the Northeast Pacific, causing temperatures to rise almost 3°C above normal. The disruption severely depressed salmon returns. Whales, sea lions and seabirds starved, and warm water creatures were suddenly being spotted off the coast of Alaska. In Puget Sound, temperatures also jumped, but the effects of the blob here proved difficult to study because of the natural variability of the Salish Sea and the heavy influence of freshwater mixing and circulation in the waterbody. Recently, computer simulations from our partners at the Salish Sea Modeling Center have begun to help scientists understand some of the complexities.

A new paper in the journal Frontiers in Marine Science analyzes results of a five-year simulation of the Salish Sea Model to assess the blob’s effects. Among its more surprising findings, the model shows that increased inflow of freshwater and nutrients from rivers and creeks was “the primary driver of increased biological activity” such as algal blooms in Puget Sound during the heatwave. The authors say that is counter to earlier assumptions that river flows were unrelated and warmer water generated by the heatwave alone was responsible. They now hope the paper will prompt further studies. Were these higher-than-normal freshwater inflows merely a coincidence? Or do they indicate the influence of heatwave impact on hydrological processes? PSI affiliate and collaborator Tarang Khangaonkar is the paper’s lead author.

Khangaonkar, T., Nugraha, A., Yun, S. K., Premathilake, L., Keister, J. E., & Bos, J. (2021). Propagation of the 2014–2016 Northeast Pacific Marine Heatwave through the Salish Sea. Frontiers in Marine Science, 1836.