If the ice suddenly disappeared, Greenland would most probably appear as an archipelago, at least until isostasy lifted the land surface above sea level once again. The weight of the ice has depressed the central area of Greenland the bedrock surface is near sea level over most of the interior of Greenland, but mountains occur around the periphery, confining the sheet along its margins. The ice cores also record human impact, such as lead from the Roman Empire. The oldest known ice in the current ice sheet is as much as 1,000,000 years old.
Computer modelling shows that the uplift would have enabled glaciation by producing increased orographic precipitation and cooling the surface temperatures. The Western and Eastern Greenland mountains constitute passive continental margins that were uplifted in two phases, 10 and 5 million years ago, in the Miocene epoch. Ice sheet formed in connection to the uplift of the West Greenland and East Greenland uplands. There was an intensification of glaciation during the Late Pliocene.
The Greenland Ice Sheet formed in the middle Miocene by coalescence of ice caps and glaciers. From about 11 million years ago to 10 million years ago, the Greenland Ice Sheet was greatly reduced in size. The presence of ice-rafted sediments in deep-sea cores recovered from northwest Greenland, in the Fram Strait, and south of Greenland indicated the more or less continuous presence of either an ice sheet or ice sheets covering significant parts of Greenland for the last 18 million years. 2.6 Twenty-first century melting events.2.4 Observation and research since 2010.2.3 General considerations on rate of change.2.2 General considerations on ice melting.2.1 The ice sheet as a record of past climates.
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