'Unprecedented' warming drives dramatic ecosystem shifts in North Atlantic, study finds

Cornwell University Chronicle: While the planet has experienced numerous changes in climate over the past 65 million years, the most significant climate change of the last 5,000 years has been in recent decades. That change is global warming. A Cornell study reports that as a result of this warming, which has caused Arctic freshwater ice to melt and flow southward, the ranges of some cold-water, northern marine species have been moving down the North American coast -- a counterintuitive finding.

The paleo-climate record shows very rapid periods of cooling in the past, when temperatures have dropped by as much as 18 degrees Fahrenheit (10 degrees Celsius) in a matter of years to decades, but "the rate of warming we are seeing [now] is unprecedented in human history," said Cornell oceanographer Charles Greene, the lead author of the study, published in the November issue of the journal Ecology (Vol. 89, No. 11).

During the past 50 years, melting Arctic ice sheets and glaciers have periodically released cold, low-salt water from the Arctic Ocean into the North Atlantic. This has led to dramatic ecosystem shifts as far south as North Carolina and extensive geographic range shifts of many plant and animal species, he said. One microscopic algal species from the Pacific Ocean, not seen in the North Atlantic for over 800,000 years, has reinvaded the North Atlantic from the Arctic Ocean during the past decade.

By reviewing climate changes in the past, the researchers were able to more clearly observe how this influx of fresher water has led to changes in ecosystems as well as the geographic distributions of species, said Greene….

This graphic shows the path of low-salinity water discharged from the Arctic Ocean in 1989 as it progresses along the continental shelf of eastern North America. From the Cornell University website