The Medieval climatic optimum (AD 700-1200) was a time of extremely favorable climate in northern Europe. Harvests were good, fishing was abundant, sea ice remained far to the north, vineyards flourished 300 miles north of their present limits, and famine was rare. This was the period of great Viking expansion from Scandinavia. Viking settlements were based on cereal grains (wheat and barley) and dairy herds (goats, sheep, and cattle).
Iceland began settling in AD 874 and soon became an independent republic. Greenland was colonized in AD 985 by Erik the Red. By the 12th century, two sizeable communities existed in southwestern Greenland.
During the Medieval climatic optimum, sea level stood at least a half meter higher in southern Florida than today from the first through tenth centuries.
Comment: In other words, sea levels in the Atlantic have fallen at least 19 inches in the last 1,000 years.