As important Atlantic currents slow down, the US East Coast faces rising oceans

The slowdown in major Atlantic currents is driving floods associated with sea levels in the northeastern United States, which are already rising due to climate change. As the planet warms, this complete collapse of Atlantic Meridian Coverage (AMOC) can raise even more sea levels.

“If AMOC collapses, this will dramatically increase flood frequency along the US coast, without strong storms.” Liping Chan Geophysical Fluid Dynamics Laboratory at the US National Oceanic and Atmospheric Administration (NOAA) in New Jersey. “Even a partial weakening [of the current] It can already have a big impact. ”

The warm waters of ice sheets and water lead to average sea level rises, due to warm waters from climate change stacked on humans, but the rates of sea level rise are not the same everywhere. For example, some coastal lands have sunk, accelerating the relative speed of sea level rise in those areas. Local sea levels are also shaped by how heat, water and salt circulate in the ocean, with warm, fresh water taking up more space than cold, salty water.

The Northeast Coast of the US has seen it Sea level rises faster Beyond the world average for decades. In addition to land subsidence, the slowdown of AMOC – transporting warm water from the lower latitudes into the North Atlantic, where it cools, salty and sinks – has long been proposed as a possible driver for this. As this cover circulation weakens, deep water along the path of current will warmly expand, pushing more water up onto the shallow continental shelf.

AMOCs naturally differ in intensity across different timescales, and climate change has contributed to slowing down as the North Atlantic and its waters become warmer and clearer in recent decades. However, it was not clear whether this slowdown was making a major difference to the sea level.

Chang and her colleagues used tidal gauge measurements along the New England coast to reconstruct local sea levels dating back more than a century. In addition to the steady rise due to climate change, they discovered a pattern of significant fluctuations between low and high sea levels every few decades. The sea level was closely matched with years when AMOC was weak, and the high sea level was closely matched, and these years also had more frequent coastal flooding.

The researchers then used two different ocean models to quantify the extent to which variations in AMOC intensity had an impact on local sea level. Although the main driver of change was steady rise due to climate change, they found that weakened AMOCs significantly increased flooding associated with sea levels. In various areas of the coast, they found that the slowdown in AMOC has been delayed by 20-50% of the flood since 2005.

Because the natural cycle of AMOC strength is largely predictable, Zhang says the findings allow researchers to predict whether there will be many floods by three years ago. This will help you make long-term decisions about infrastructure and emergency preparation.

“It shows that AMOC is really important. [sea level rise]”I say Chris Hughes He was not involved in research at the University of Liverpool in the UK. “It’s not just models and theories, it’s actually in the real world.”

It is not clear how much of the recent weakening of AMOC is due to climate change or natural changes. However, the findings add support for predictions that if AMOC collapses completely in response to climate change, much of the US East Coast could surge at sea level.

Hughes says that if the current almost collapses, the sea level can rise by about 24 centimeters. “It doesn’t sound that loud, but it doesn’t need to go up much to get a big effect.”