Atlantic Meridional Overturning Circulation (AMOC)
Download the full MCCIP Science Review 2017 for Atlantic Meridional Overturning Circulation (PDF)
MCCIP reported in 2006 that:
- a 30% decline in the AMOC has been observed since the early 1990s based on a limited number of observations. There is a lack of certainty and consensus concerning the trend;
- most climate models anticipate some reduction in strength of the AMOC over the 21st century due to increased freshwater influence in high latitudes. The IPCC project a slowdown in the overturning circulation rather than a dramatic collapse.
And in 2017 that:
- a substantial increase in the observations available to estimate the strength of the AMOC indicate, with greater certainty, a decline since the mid 2000s;
- the AMOC is still expected to decline throughout the 21st century in response to a changing climate. If and when a collapse in the AMOC is possible is still open to debate, but it is not thought likely to happen this century.
And also that:
- a high level of variability in the AMOC strength has been observed, and short term fluctuations have had unexpected impacts, including severe winters and abrupt sea-level rise;
- recent changes in the AMOC may be driving the cooling of Atlantic ocean surface waters which could lead to drier summers in the UK.
What we have learned:
Measuring variability of the AMOC is key to understanding any trends and wider implications for the UK such as extreme winters or the seasonal-to-decadal variations in the climate.
Atlantic Meridional Overturning Circulation (AMOC). Red colours indicate warm, shallow currents and blue colours indicate cold, deep return flows. Modified from Church, 2007, A change in circulation? Science, 317(5840), 908–909. doi:10.1126/science.1147796
Please cite this document as:
McCarthy, G.D., Smeed, D.A., Cunningham, S.A. and Roberts, C.D. (2017). Atlantic Meridonal Overturning Circulation. MCCIP Science Review 2017, 15-21, doi:10.14465/2017.arc10.002-atl