Greenland ice melting threatens Northeast United States and Canada

The thawing of Greenland in this century will push more seawater towards the threatened coastline of New York, Boston, Halifax and other cities of the Northeast United States and Canada than previously thought, According to a new study under the direction of the National Meteorological Research Center (NCAR).

The study, published May 29 in the journal Geophysical Research Letters, found that if Greenland ice melted at a moderate or rapid pace, the circulation of seawater until 2100 would cause sea level in the coast. North America's North Sea is 12 to 20 inches taller (about 30 to 50 centimeters) compared to other coastal areas. Research based on recent reports of rising sea levels and global warming will adversely affect North America, and the results of the study show a more serious situation than previously thought.

Aixue Hu, NCAR researcher and lead author, said: 'If the ice melting rate in Greenland continues to increase, we will see a significant impact in this century on the Northeast coast. United States, due to rising sea levels'.

A study in Nature Geoscience in March warned that rising sea temperatures would displace sea currents and push the sea level in the Northeast to 8 inches (20cm) higher than the average increase. bridge. But this study does not include the additional effect of melting ice in Greenland. With the average melting speed of ice in this area, changes in seawater circulation will be accelerated and 4 to 12 inches (10 to 30 cm) of seawater will be added to densely populated areas in the Northeastern North America. In more remote areas in Northeast Canada and Greenland, sea levels may be higher.

Scientists are very interested in measuring the rate of sea level rise in this century in part because of complicated processes inside sea ice sheets. The 2007 assessments of the Intergovernmental Panel on Climate Change predict that the sea level will increase by an average of 7 to 23 inches (18 to 59 cm) this century, but scientists believe that the This increase will be higher because motivational factors within the icebergs seem to accelerate the melting speed in recent years. The new study is funded by the US Department of Energy, NCAR and the National Science Foundation. The study was conducted by scientists at NCAR, the University of Colorado at Boulder, and Florida State University.

Computer simulations show that the sea level will increase by 10 centimeters in the densely populated areas of the northeastern United States compared to previous thoughts. (Photo: Geophysical Research Letters)

The amount of water dissolved?

To assess the impact of Greenland ice melt on ocean currents, Hu and co-authors used the Climate Change Model, a NCAR computer model that simulates global climate. They consider three situations: the speed of melting ice continues to increase by 7% a year, like in recent years, or the speed of ice has slowed down with an increase of 1 or 3% a year.

If the speed of ice melting in Greenland slows with a 3% increase a year, computer simulations indicate that the amount of seawater melting from the ice blocks will change the current and direct about 1 minute (0.3048 meters) of seawater to in the northeastern United States by 2100. Although the research team did not measure the average rate of global sea level rise, their simulation showed that melting ice from Greenland alone in the 3% situation would increase ink levels. seawater about 21 inches (54 cm).

If the annual increase in ice melt rate drops to 1%, the amount of water dissolved will increase the sea level in the Northeast to more than 8 inches (20cm) as the study in Nature Geoscience said. But if the melting speed continues at 7% as of now until 2050, the study shows that the Northeast coast will have a 20-inch (50cm) increase compared to the global average. However, Hu also said other studies show that the 7% situation will be less likely to happen.

In addition to the sea level rise, Hu and co-authors also found that if the ice melt rate in Greendland continued to increase at 7% a year, the amount of fresh water absorbed into the North Atlantic would be enough to weakens ocean currents to bring warm water to Antarctica. Ironically, the weakening of ocean currents will help Antarctica avoid some of the effects of global warming and lead to sea ice recovery in Antarctica by the end of the century.

Why is it the Northeast?

The North East coast of North America is directly influenced by the impact of melting ice in Greenland, because the ocean current acts as a conveyor belt to carry water across the Atlantic Ocean. The ocean currents bring warm Atlantic water from the tropics to the north , where it cools and settles down to the dense cold water. Therefore, the current sea level in the North Atlantic is lower than the North Pacific (where there is no dense cold water) about 28 inches (71 cm).

If the Greenland thaw increases from 3 to 7% per year, the additional fresh water will hinder some of the northbound conveyor belt. This will reduce the concentration of deep and dense water. Instead, the deep water will be warmer, expand and push the surface higher in some parts of the North Atlantic.

Unlike water in baths, the water in the ocean is not evenly distributed. The sea level may vary several minutes between regions, depending on factors such as ocean currents or the degree of compression of deep water.

Gerald Meehl, co-author of the study, said: 'The sea level will not increase steadily when the Earth warms. The sea will push water in certain directions, so some areas will have sea level rise higher than the global average. '

References:
Aixue Hu, Gerald Meehl, Weiqing Han, and Jianjun Yin.Transient Response of the MOC and Climate to Potential Melting of the Greenland Ice Sheet in the 21st Century.Geophysical Research Letters, May 29, 2009 DOI: 10.1029 / 2009GL037998