A new paper has been published by Sicre et al in Earth and Planetary Science Letters entitled: 'Decadal variability of sea surface temperatures off North Iceland over the last 2000 years.'

The Abstract states:
Ocean variability at decadal time-scales remains poorly described partly because of the scarcity of high temporal resolution marine records. Here, we present a reconstruction of Sea Surface Temperatures (SSTs) over the past two millennia at unprecedented temporal resolution (2 to 5 years), from a marine core located off North Iceland. Alkenone paleothermometry was used to infer SST variability, and tephrochronology to build the age model. Spectral analyses of the SST signal indicate intermittent 20–25 year oscillations, with periods of strong and weak power, that are likely reflecting the ocean response to wind forcing, presumably the North Atlantic Oscillation (NAO). Warmer SSTs and paleo-magnetic proxy data, between 1000 and 1350 year A.D., overlapping the Medieval Warm Period (MWP), suggest enhanced heat transport across the Denmark Strait by the North Icelandic Irminger Current (NIIC). This is in contrast with the subsequent period, which includes the Little Ice Age (LIA), showing continuous cooling towards the 20th century. Reduced NIIC flow through the Denmark Strait likely resulting from higher freshwater and sea ice export from the Arctic would account for the observed colder conditions.

Keywords: Decadal variability; Sea surface temperature; North Atlantic; Alkenones; Medieval Warm Period; Little Ice Age; Iceland

The authors state in the Discussion:

"A remarkable feature of the North Icelandic SST record is the abrupt increase of around 1–1.5 °C occurring within a decade around 980 A.D., maybe imputable to the onset of the MWP. This sustained warm period, lasting for several centuries, ends by a sharp cooling around 1350 A.D., following a brief cold episode around 1250 A.D. The same pronounced centennial-scale warming, though not exactly synchronous, has been documented by the distant records from the Sargasso Sea (Keigwin, 1996), the Eastern sub-tropical Atlantic (deMenocal et al., 2000) and estuarine sediments of Chesapeake bay (Cronin et al., 2005), confirming its widespread occurrence in the North Atlantic region."  Source