Global Warming is Hastening Earth’s Ocean Circulation System

New Delhi: A recent study published by the multidisciplinary science journal Science Advances says that the ocean circulatory system has started to pick up speed. In a paper titled ‘Deep-reaching acceleration of global mean ocean circulation over the past two decades,’ published on February 5, researchers looked at the rapid speeding up of ocean currents. Over the past 25 years, ocean currents have seen a rapid speeding up and a major part of this is due to global warming.

There is a connected system of massive currents in oceans, popularly known as the great ocean conveyor belt. In a sense, the conveyor belt connects water of all the oceans of the planet, and this water is in motion—circulation. This ocean current circulation is a phenomenon by way of which if someone starts by deep-diving into the Atlantic Ocean, the person will find themselves back at the Atlantic having traversed through all the oceans. This circulatory system redistributes heat and nutrients around the globe and has a powerful effect on climate. This circulation transports warm water from the tropics to polar regions and cold water from the poles back to warmer climes.

The study was led by Shijan Hu, a researcher associated with the Chinese Academy of Sciences, along with collaborators from Australia, China and the United States. The researchers used a global network of devices named Argo Floats along with other data sets to conduct their research.

The authors conclude that between 1990 and 2013, the energy of ocean currents has increased by almost 15% per decade. The estimate, if real, could have huge consequences — it could affect jet streams, weather patterns and also the amount of heat stored in the ocean’s depths.

The researchers write that 76% of the oceans are speeding up when the upper 2,000 meters of oceans are taken into account. Also, the increase in speed is most intense in tropical oceans, especially the Pacific.

The primary reason for this could the near-2% rise in wind speeds per decade, which has intensified circulation as deep as 2,000-3,000 feet in oceans that are affected. Research found that the 2% per decade increase in wind speed has translated into about a 5% increase per decade in the current speeds of oceans.

In a scenario where global warming is approaching a tipping point, the speeding up of global winds also occurs. This was expected to hit a peak at the end of this century, with researchers writing that “the global circulation system as a whole has been accelerating substantially since the last decade of the 20th century.” Their findings indicate that the earth is more sensitive to climate change than simulations that the scientific community have achieved.

Scientists are not sure enough what consequences this increase in kinetic energy of global ocean tides would have. But this surge may have consequences along the eastern coasts of continents where many currents have intensified. In some cases, the result has been the damage of ocean hot-spots, which is destruction of marine lives.

Though the researchers are uncertain whether ocean current speed change is solely due to greenhouse gases and associated global warming, they have said that the changes are far greater than what would happen with natural variability. Moreover, this change is not observed in isolation. Of late, there have been large-scale changes observed in the world’s oceans.