Environment and Energy

Scientists: Sea Level Rise will Swamp Subways

Scientific predictions of sea level rise in New York City just keep getting higher. In 2006, Vivian Gornitz of Columbia University predicted a rise of from 24 to 108 centimeters by 2080. She noted that many of our subway and road tunnel entrances are less than 3 meters above sea level, leaving them vulnerable to flooding during a “hundred-year” storm. But the effects of global warming make the situation even worse, raising overall water levels so that less severe, more frequent storms will put them at risk (Global and Planetary Change vol 32, p 61). If sea levels had been around half a metre higher during a storm in December 1992, the tunnels would have been inundated, she said then. The most recent predictions are more alarming.They pose another cause of rising sea levels, over and above the melting ice at the poles.

 

Reports New Scientist Magazine:

A new study shows that sea level rise due to climate change in the next 100 years will be disproportionately high around New York and other cities of northeast US.

Today, the sea level along the east coast of the US is lower than elsewhere, whereas further offshore the level rises sharply.

This anomaly is caused by the balance of forces required for the flow of the strong Gulf Stream and North Atlantic Current, both of which contribute to the Atlantic meridional overturning circulation (AMOC).

The AMOC transports warm surface waters to the high northern latitudes, where the currents cool and sink and then flow back southwards across the Equator.

Already, some studies have shown that the AMOC slowed by about 30% between 1957 and 2004, and it is expected to slow down further because of global warming.

This slowdown, besides possibly endangering the mild climate of northwest Europe, will remove the dynamic forces that keep the sea level anomalously low along the US east coast.

Half a metre

Jianjun Yin of Florida State University and colleagues used climate models used by the Intergovernmental Panel on Climate Change (IPCC) to study how changes to the AMOC will affect sea levels.

They found that, for a scenario with high greenhouse gas emissions, the sea level rise solely due to thermal expansion of the oceans could reach 52, 51 and 44 centimetres around Boston, New York and Washington D.C. respectively, by 2100.

This would pose a particular threat to New York, as some parts of lower Manhattan are only about 1.5 metres above sea level.

In contrast, other coastal cities like San Francisco, London and Tokyo will be impacted far less, because of the local ocean conditions.

Read more: here

 

February 6, 2009

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