Spielhagen, R.F., Werner, K., Sorensen, S.A., Zamelczyk, K., Kandiano, E., Budeus, G., Husum, K., Marchitto, T.M. and Hald, M. 2011. Enhanced modern heat transfer to the Arctic by warm Atlantic water. Science 331: 450-453.
Based on the identity and abundance of different planktic foraminifer associations found in a sediment core extracted from the Fram Strait of the Atlantic Ocean off the coast of Western Svalbard (78°54.94'N, 6°46.04E), Spielhagen et al. determined that the peak summer warmth of the MWP (~AD 750-1100) was about 1.8°C less than the peak summer warmth of the CWP.