The motion of the ocean isn't just a fantastic phrase to pop into song lyrics—ocean currents dictate temperatures, sea levels and even weather all over the Earth. And researchers monitoring them have now made some predictions about how Earth's climate will likely change over the next few decades to which we should pay heed.
Scientists from the National Oceanography Centre (NOC) and the University of Southampton have collated evidence that the global climate is on the verge of a broad-scale change that could last some decades. Their findings are predictions drawn from observations of how ocean currents affect surface temperatures of the Atlantic Ocean.
Models predict that the cooling of the Atlantic Ocean will ultimately have climatic repercussions in areas surrounding this ocean. The northeast coast of the United States is likely to experience an acceleration in sea-level rise, Britain and Ireland will probably experience drier summers, and developing countries in the Sahel region may experience drought.
Since the Atlantic Ocean seems to be cooling, we could be entering a new, chillier climate phase—about half a degree cooler. This would temporarily counteract the effect of global temperature rise, and may result in fewer hurricanes hitting the United States.
Lead author Dr. Gerard McCarthy from the NOC said: "Sea-surface temperatures in the Atlantic vary between warm and cold over time-scales of many decades. These variations have been shown to influence temperature, rainfall, drought and even the frequency of hurricanes in many regions of the world. This decadal variability, called the Atlantic Multi-decadal Oscillation (AMO), is a notable feature of the Atlantic Ocean and the climate of the regions it influences."
The AMOs that McCarthy refers to are the result of heat moving northwards via Atlantic Ocean currents. When the ocean moves heat in its currents, it naturally affects the ocean surface temperature which, in turn, has a noticeable effect on the climate. These oscillations result in climate changes that typically last for timescales of around 20 to 30 years.
The Atlantic is set to enter a negative AMO phase. This means that the present Atlantic currents are weaker than previous currents. Less heat is carried northwards from the tropics towards Europe, resulting in a slightly lower global temperature.
Rapid Moorings being deployed so that they can measure the rate of ocean currents via National Oceanography Centre
These predictions have been made using data from a network of sensors called the RAPID array that record how fast the Atlantic is flowing. The RAPID array has only been collecting data for about ten years, so to supplement this data the scientists used 100 years of sea-level data to create meaningful models of the ocean currents, and to predict what they're likely to do next.
Dr. David Smeed, from the NOC and lead scientist of the RAPID project, adds: “The observations of AMOC from the RAPID array, over the past ten years, show that it is declining. As a result, we expect the AMO is moving to a negative phase, which will result in cooler surface waters. This is consistent with observations of temperature in the North Atlantic.”
Professor Ian Wright, director of science and technology at the NOC, said: "This work clearly emphasizes the critical role of the ocean in driving decadal-scale changes in climate that has very real human consequences, as well as the continued need for long-term measurement of ocean change at critical sites around the world"
[Via National Oceanography Centre, University of Southampton]
