A new study by the Woods Hole Oceanographic Institute (WHOI) examines the impact of the main currents in the North Atlantic on sea level in the northeastern United States. A study published June 13 in the journal Geophysical Research Letters, considered as the strength of the Atlantic meridional tipping (AMOC) – a conveyor of flows that move warmer waters to the north and colder waters to the south in the Atlantic – and historical records of sea level in coastal New England
“Scientists have previously noted that if the AIOC is stronger at certain times of the year or year, the sea level in the northeastern United States decreases. If the AIOC weakens, the average sea level rises significantly, ”says Chris Picchu, a physical oceanographer at WHO and the Author of the paper author. “For example, in the winter of 2009-2010. We saw that AIOC weakened by 30 percent. At the same time, the sea level in our region has grown by six inches. That doesn't sound like much, but a half-foot sea level rise that has been sustained for months can have serious consequences for the coastal zone. ”
“But it’s unclear whether these two things are related – the sea level on the coast and AMOC – cause and effect,” adds Picuch. Although the study confirmed that the AMOC intensity and sea level appear to be changing at the same time, it turned out that neither of them causes immediate changes in the behavior of the other. Instead, both seem to be controlled simultaneously by the variability of the main weather conditions in the North Atlantic, such as the North Atlantic Oscillation (NAO).
“Changes in NAO change both AMOC and sea level separately,” says Picuch. “As the NAO changes, it affects the trade winds blowing from the east across the tropical Atlantic. When the NAO is strong, the trade winds are stronger than usual, which in turn reinforces the AMOC. But at the same time, the western winds over New England are also stronger than usual. Together with the unusually high air pressure on the northeast coast, this lowers the mean sea level. It is wind and pressure that drive both phenomena. "
According to Peckuch, such a study was impossible until recently. Over the past few decades, satellite imagery has given scientists a record of movement on the surface of the ocean, but could not detect currents below the surface. Beginning in 2004, however, an international team of scientists began to maintain a chain of instruments that stretch across the Atlantic between Florida and Morocco. The instruments, collectively referred to as the RAPID array, contain various sensors that measure currents, salinity and temperature. “RAPID does not resolve the details of each individual flow along the way, but it gives us the total amount of ocean behavior that AMOC represents,” notes Picchu.
These findings are especially important for residents along the northeast coast of the United States, he adds. Existing climate models suggest that sea level on a global scale will increase in the next century due to climate change, but this sea level rise on the coast of New England will be higher than the world average. Scientists have traditionally assumed that sea level rise in the northeastern United States in the future is inextricably linked to the weakening of the AIOC, which climate models also predict. But given the results of the study, this assumption may need to be revised, says Pecucci. “The problem now is that we only have about 13 years of working AMOC data. To better understand how these two things relate to each other in the long run, we need to wait a longer period of time. ” records of observations will become available, ”he says.
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Christopher J. Pichuch et al., As the sea level in New England is associated with the turning of the Atlantic meridion at 26 ° N, Geophysical Research Letters (2019). DOI: 10.1029 / 2019GL083073
There is no direct link between North Atlantic currents and sea level along the coast of New England (2019, June 14)
restored June 14, 2019
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