Wednesday, 30 April 2014


Can you predict the Atlantic Meridional Overturning Circulation?   Or would you like to win a RRS James Cook mug?    If your answer to either of these questions is yes then read on and enter our competition.

The AMOC at 26°N from 2004 to 2012.
How has it changed  since then?
Earlier this year we published a paper describing the evolution of the Atlantic Meridional Overturning Circulation (that is something of a mouthful so we usually call it the AMOC) (ref. 1).     Its been quite variable but the average trend has been downward.    Our colleagues at the University of Reading have published a paper predicting that it will continue to decline (ref. 2).  Are they right? *

Perhaps you have a model that can calculate the AMOC?   Or would you like to make a guess?  Either way we would like to hear from you.

RRS James Cook mug to be awarded to he winner of our competition
Please let us know your estimate for the mean AMOC at 26°N for the period 1st October 2012 to 31st September 2013.     At the end of the cruise we will make a preliminary calculation based on the data we have collected.    The winner of the competition will be the estimate that is closest our preliminary value.    We calculate the AMOC in units of Sverdrups, with one Sverdrup being equal to one million cubic metres per second.   To help you make your estimate here are the mean values for previous years  (these are averages for 12 months starting in April each year).

  Year     2004  2005  2006  2007  2008  2009  2010  2011  
  AMOC(Sv) 17.8  20.1  19.5  18.0  17.5  12.9  16.7  17.5

The best estimates will be listed on our blog and if you win we will ask you for your address so we can send you your RRS James Cook mug (please don't post your address now).

The rules of the competition are:

1.  Entires should be made by adding a comment to this post or by email to with the subject "JC103 competition" and received no later than 31st May 2014. Alternatively you can tweet your entry using  .

2.  Only one entry per person please.

3.  The estimate closest to our preliminary calculation will be the winner.  In the event of a tie a draw will be held to decide who will receive the RRS James Cook mug.

4.  The Principal Scientist's decision will be final and no appeals will be considered

*Jon Robson and co-authros would probably wish us to point out that they were not making a prediction for a particular year but suggesting that the average trend will be downwards.    So even if the AMOC goes up now that would not necessarily mean that they are wrong.    We need to wait a few more years before we can judge that.

(1) Smeed, D.A., McCarthy, G.D., Cunningham, S.A., Frajka-Williams, E., Rayner, D., Johns, W.E., Meinen, C.S., Baringer, M.O., Moat, B.I., Duchez, A., Bryden, H.L., 2014. Observed decline of the Atlantic meridional overturning circulation 2004-2012. Ocean Sci. 10, 29–38.

(2) Robson, J., Hodson, D., Hawkins, E., Sutton, R., 2013. Atlantic overturning in decline? Nat. Geosci. 7, 2–3.


  1. 1st guess in from Renellys Perez (via @MotherAtSea on Twitter), 15.8 Sv!

    1. And another from C Florindo Lopez (via @PhysicalOcean on Twitter), 18.3 Sv

    2. Another from Aurelie Duchez: I say 18.2 Sv and I am aiming for the glory AND the mug :)

  2. Another tweeted entry from @sheldonbacon
    "19.4 Sv. I'm aiming for glory rather than the mug."