All clear for Europe's water heating?

Observation system for the Atlantic circulation provides initial results

North Atlantic Circulation © NASA / GSFC
Read out

The Atlantic circulation is responsible for the mild climate of Europe. The likelihood of a possible "collapse" has been discussed intensively for years. Now, for the first time, an international team of scientists is in a position to continuously monitor the daily fluctuations in the strength of Europe's water heating. In the science journal Science, the researchers present the analyzes of the data from the first year of measurement. Result: So far, there are no signs of weakening the Atlantic circulation.

The researchers from the United Kingdom, Germany and the United States have installed a unique observation system that can detect the fluctuations of the Atlantic Meridional Overturning Circulation (MOC) at an early stage. The system will allow scientists to verify model simulations of MOCs. In addition, it will feed into more realistic climate forecasts, which are essential for adaptation planning.

In March 2004, the scientists built their observation system on the 26th parallel across the Atlantic from the African coast to the Bahamas. Since then, the instruments have provided continuous series of measurements of temperature, salinity and density. Combined with measurements of Gulf Stream in the Strait of Florida (by American scientists from NOAA) and with satellite measurements of wind-driven currents over the 26th parallel, the MOC can be determined daily.

MOC still stable

The results in Science show that the extraordinary observation system works effectively and provides surprising results. The overall variability of the measured MOC in the Atlantic is very large: from four Sverdrup to 35 Sverdrup. Sverdrup (Sv) is the measure of ocean current, with Sv corresponding to one megaton of water per second. The annual average MOC was calculated at approximately 19 sverdrup, which is consistent with previous estimates.

"There is still no sign of a slowdown in MOC. The large fluctuations are also the reason that was diagnosed earlier, a mitigation has already taken place. It happened to be measured at a time when the circulation was just weak, "explains Professor Jochem Marotzke of the Max Planck Institute for Meteorology. display

With the observation system at the 26th parallel, the annual average of the MOC can be observed exactly up to 1.5 Sv or up to eight percent of the mean value. This is enough to detect large, abrupt changes in circulation that are critical to adaptation planning to climate change.

(idw - Max Planck Institute for Meteorology, 17.08.2007 - DLO)