Sea levels in northeastern United States rose in an unprecedented way during 2009-2010. Researchers show that within this two year period, the coastal sea level north of New York City jumped by 128 mm (five inches), something unheard during the entire history of the tide gauge records.
According to the findings published in the Nature Communications journal, statistical analysis indicates that it is a 1-in-850 year event, but the climate models suggest it will become more common this century, as the rate of atmospheric carbon dioxide will continue to increase.
“When coastal storms occur, extreme sea levels can lead to elevated storm surge. In addition to long-term and gradual sea level rise, coastal communities will need to prepare for short and extreme sea level rise events,” assistant professor and co-author Jianjun Yin of the University of Arizona told BBC.
Scientists at the University of Arizona and National Oceanic and Atmospheric Administration in New Jersey, who studied the tidal levels along the east coast of the US and Canada, discovered that the unusual spike in sea level was a result of changes in ocean circulation, this being the first study to link the extreme event with ocean currents that brings heat from the tropics toward the colder, saltier waters of the North Atlantic.
In a parallel research that was taking place in the same time, according to Psys.org, another group of scientists reported that the Atlantic Meridional Overturning Circulation (AMOC) had a 30 percent decline in strength in 2009-2010. They say the decline started just two months before the spike in sea level and this helped the teams understand the connection. To me, it was like putting together a puzzle,” said first author Paul Goddard from University of Arizona.
In addition to the weakening current, during 2009-2010 the region’s atmosphere was in a very negative phase called the North Atlantic Oscillation, which changes the wind patterns and pushes the water onto the northeast coast. Although he North Atlantic Oscillation is changing between positive and negative states, the Atlantic Meridional Overturning Circulation is still weak.