An international team of scientists led by Julia Parrish of the University of Washington has linked the unexplained mass death of birds on the US West Coast to rising ocean temperatures due to global warming. According to the conclusion of experts, the animals died of starvation caused by the fall in the content of zooplankton in the waters of the Pacific Ocean. The results of the study are reported in a press release on Phys.org.
In 2014, the coast from California to British Columbia was strewn with 250-500 thousand dead Aleutian fawn (Ptychoramphus aleuticus). Volunteers noted the location of the carcasses and the date they were found by entering information into a special database. The researchers combined this information with data on water temperature, ocean circulation and the abundance of the food supply for birds - zooplankton (krill and copepods).
It turned out that in 2013-2015, the surface waters off the Pacific coast warmed sharply due to a decrease in heat outflow into the atmosphere. Since zooplankton prefer cooler water, this has led to the undermining of the birds' food supply. Until the summer of 2014, a cold wedge, rich in food, remained off the coast of North America. However, ocean circulation changed in the fall and the wedge disappeared, resulting in the deaths of birds migrating south from British Columbia.
According to scientists, such cases will be repeated, as the effects of global warming become more pronounced. In the future, experts say, the entire northern part of the Pacific Ocean is likely to become significantly warmer, and the event of 2014 is a kind of "natural experiment", the results of which can predict the consequences.