According to scientists, the gradual but ever-increasing melting of the Greenland ice sheet, caused by the onslaught of greenhouse gases, is causing the Gulf Stream to circulate at a slower rate. Man-made global warming is seen to be a major arbiter of the thinning and disappearance of ice around the world. Scientists warn that further weakening in the Earth’s ozone layer from chlorofluorocarbons, refrigerants, and carbon pollution will cause worldwide ice melts, putting more water in the oceans. The melting of the Greenland ice sheet would advance the desalinization of currents, thus changing weather systems by the perturbation of the North Atlantic Ocean, harming marine ecosystems and accelerating shoreline erosion.
Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research launched a study regarding the oscillations of the North Atlantic Current, published in the latest issue of the journal Nature Climate Change. He stated that it is a conspicuous notion that the areas in the North Atlantic have been decreasing in temperature during the last 100 years, while regions in other parts of the world have recorded temperatures rising at an exponential rate. Though, Rahmstorf stated previous research has indicated that the sluggishness of the North Atlantic oscillation and circulation may be reason for this finding. He explained he has found evidence that the global current has most definitely been weakening since the beginning of the 20th century, increasing its impact since 1970.
Scientists have only ever measured ocean temperatures on the surface, therefore, long-term measurements of direct ocean currents are deficient. By using only sea surface temperature readings and atmospheric changes to surmise the rate of Gulf Stream changes, Rahmstorf found that the exploitation of this data has led scientists to believe that the cause was solely from temperature variations in the North Atlantic below the polar ice cap. Though, he began to use data collected from ice cores and lake and ocean sediments to deduce the temperatures from millennia ago. He and his team found that since the year 900 A.D., changes in temperatures were unprecedented, leading to the finding that the change in the Gulf Stream is undoubtedly caused by man-made global warming.
Jason Box, a researcher at the Geological Survey of Denmark and Greenland, stated freshwater that is being injected into the North Atlantic Current is disturbing the normal ocean circulation. The overturning of the Atlantic Ocean is causing differences in water density. From the south, warm, thus lighter water flows towards the north, where cold, hence heavier water sinks towards the lower depths of the ocean and flows back south. The salinity levels in the water can also change these factors. When ice is melted, a large quantity of fresh water can offset the equilibrium of levels of salt and fresh water in the ocean. This causes the oscillations in the world’s oceans to slow down, causing atmospheric currents, like the Gulf Stream, to slow in conjunction.
Michael Mann, a researcher at Penn State University, stated common climate models are grossly underestimating the changes in the Gulf Stream. This is attributed to the lack of previous sufficient data that only measured sea surface temperatures. “They do not properly account for Greenland ice sheet melt,” he said. Rahmstorf believes that if the Atlantic overturning continues to slow, the Gulf Stream will become weaker, having a negative effect on marine ecosystems. Therefore, coastal settlements that rely of fisheries for their main source of income will be crippled. Moreover, large coastal metropolises like New York City will be victim to massive flooding from the stark rise in sea levels from more water being put into the ocean from the Greenland ice sheet. Furthermore, the Gulf Stream can influence weather on both the North American and European continents, causing great temperature fluctuations.
If the melting of the Greenland ice sheet weakens the North Atlantic Current too much, or even completely breaks it down, changes in temperature in the oceans throughout the seasons will be much different than they are today. This could even destroy the Gulf Stream all together and be a tipping point for the well-being of the Earth.
By Alex Lemieux
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