Midway through the past decade, as many as one million seabirds died in less than a year, and scientists say they now know why: warm ocean water caused by global climate change.

Researchers say it was one of the largest mass die-offs in recorded history. It happened between 2015 and 2016 in the northeast Pacific Ocean.

Scientists say the seabirds, called murres, were dying of starvation and washing up on the west coast of North America but they didn’t know why.

According to CNN, scientists say the deaths were the result of a section of warm ocean water they are now calling "the Blob."

It was a 1,600 kilometer stretch of ocean that warmed by 3 to 6 degrees Celsius. (Para5) It was caused by a severe marine heat wave from 2013 to 2016.

The warming of this patch of ocean led to a drop in microscopic algae that many animals depend on for food and the bloom of harmful algae that killed many animals. 

Sea lions, tufted puffins and baleen whales are other animals that experienced mass die-offs with these changes.

"The Blob" caused a ripple effect among the murres. Without enough food, the birds had difficulties with breeding and reproduction, which led to a decline in the population.

This comes as NASA and the National Oceanic and Atmospheric Administration (NOAA) recently released a study saying 2019 was the second hottest year on record and the 2010’s the hottest decade on record. 

The Earth’s temperatures have been rising every year. According to the study, the last 5 years were the hottest with 2016 taking the lead and 2019 coming in a close second.

It is also expected that 2020 will continue the warming trend.

CNN reports another mass of warm ocean water the size of the U.S. state of Texas is forming off the coast of New Zealand.

This patch of water is about 5 degrees celsius warmer than the average.