Read here. Map source here. Using sediment cores and two different techniques of analysis, scientists confirm in a peer-reviewed study that Medieval Warming peak sea surface temperatures adjacent to Greenland were some 3°C higher than modern temperatures, both in the winter and summer. No wonder Erik the Red found Greenland so agreeable and attractive.
"The authors developed a high-resolution record of ocean and climate variations during the late Holocene in the Fram Strait.....based on detailed analyses of a sediment core recovered.....sea surface temperature (SST) histories were "nearly identical and show oscillations between -1°C and 5.5°C in winter and between 2.4°C and 10.0°C in summer,".....the mean SSTs of summers were warmer than those of the present about 80% of the time, while the mean SSTs of winters exceeded those of current winters approximately 75% of the time.....The highest temperatures of all were recorded in the vicinity of 1320 cal. years BP, during a warm interval that persisted from about AD 500 to 720 during the very earliest stages of the Medieval Warm Period"
Additional climate history postings.