Researchers can predict Atlantic Meridional Overturning Circulation

Jan 09, 2012

Climate scientists around Dr. Daniela Matei and Prof. Dr. Jochem Marotzke from the Max Planck Institute for Meteorology and Prof. Dr. Johanna Baehr from Hamburg University have now shown for the first time that the strength of the Atlantic Meridional Overturning Circulation at 26.5 °N can be skillfully predicted for up to four years. Their results have been recently published in Science.

The Atlantic Meridional Overturning Circulation (AMOC) - colloquially known as "Gulf Stream" - transports warm surface waters into the high latitudes, where they cool, sink and return southwards at depth as cold North Atlantic Deep Water. Variations in AMOC can significantly affect the northward ocean heat transport and therefore the European and North Atlantic climate. Through its influence on sea surface temperature (SST), AMOC can further impact climate phenomena such as Sahel droughts or the frequency of Atlantic hurricanes. Therefore, it is of outmost importance to be able to predict these climate variations on a time horizon from years to decades. Multi-year climate predictions have so far been limited to predicting surface temperature variations and hurricane frequency, but have not addressed the prediction of any dynamical quantity such as the AMOC.

In the near term (inter-annual to decadal timescales), climate variations are influenced by both anthropogenic forcing and natural variability. This is why the near-term climate prediction models must be started (“initialized”) from the present state of the ocean.

The skill of any prediction system is assessed retrospectively, by performing the so-called “hindcast” or “retrospective forecast” and comparing them with observations. In the present study, ensemble hindcasts have been performed starting in January of each year between 2004 and 2007. The AMOC strength in the hindcasts closely follows the observations for up to four years.

The results of the coupled atmosphere-ocean-model ECHAM5/MPI-OM of the MPI-M have been evaluated against the only continuous available observations of the AMOC over the period April 2004 to March 2009. The AMOC observations were and will be performed in the RAPID-MOC project.

The good agreement between the hindcasts and the observations has motivated Dr. Daniela Matei and her colleagues to also produce AMOC forecasts (more details on the method in the original publication). An ensemble of nine forecasts spanning 10 years has been constructed for each of the Januaries from 2008 to 2011. For all start years the ensemble mean forecasts until 2014 indicate a generally stable AMOC. However, the forecast initialized in January 2010 shows a pronounced minimum in March 2010. This brief minimum was induced by an extremely negative NAO (North Atlantic Oscillation) during the winter 2009/2010.

According to the findings of the working group, the AMOC predictive skill arises predominantly from the basin-wide upper-mid-ocean geostrophic transport. The results of the study demonstrate that the skill of climate prediction arises not only from the large ocean thermal inertia, but also from the long timescales of internal ocean dynamics.

The work was supported by the BMBF "Nordatlantik II" project and the Cluster of Excellence "CliSAP" (Integrated System Analysis and Prediction) of the University of Hamburg.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: Multiyear Prediction of Monthly Mean Atlantic Meridional Overturning Circulation at 26.5°N, Science, 6 January 2012:
Vol. 335 no. 6064 pp. 76-79. DOI: 10.1126/science.1210299

Attempts to predict changes in Atlantic Meridional Overturning Circulation (AMOC) have yielded little success to date. Here, we demonstrate predictability for monthly mean AMOC strength at 26.5°N for up to 4 years in advance. This AMOC predictive skill arises predominantly from the basin-wide upper-mid-ocean geostrophic transport, which in turn can be predicted because we have skill in predicting the upper-ocean zonal density difference. Ensemble forecasts initialized between January 2008 and January 2011 indicate a stable AMOC at 26.5°N until at least 2014, despite a brief wind-induced weakening in 2010. Because AMOC influences many aspects of climate, our results establish AMOC as an important potential carrier of climate predictability.

add to favorites email to friend print save as pdf

Related Stories

Call for network to monitor Southern Ocean current

Aug 17, 2007

The senior science advisor to the World Climate Research Programme (WCRP) has called for the establishment of a Southern Hemisphere network of deep ocean moorings to detect any change in ocean circulation ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...