Ice on Greenland - 20 million years earlier than previously thought
The Earth had glaciers in parts of the northern hemisphere as far back as 38 million years ago, much earlier than was previously thought.
That is the conclusion of University of Southampton scientists based at the National Oceanography Centre, Southampton (NOCS), reported online by the science journal Nature this week.
The research indicates for the first time that there was glacial ice, probably of restricted extent, on Greenland during a time when CO2 levels are thought to have been significantly higher than pre-industrial levels. The findings therefore have implications for our understanding of future climate change in an increasingly CO2-rich world. The next task is to investigate ice extent and stability during this geological analogue for the future.
The Earth went through a profound change in climate during the transition between the Eocene and Oligocene periods (around 34 million years ago) when the Antarctic ice sheets expanded to close to their modern size. But the existence of northern polar ice had only previously been demonstrated back to the Miocene period (around 15 million years ago).
The new research provides evidence for an earlier development of northern hemisphere ice, linked to glaciers on East Greenland which are identified as the likely source of `ice-rafted' debris found in sediments drilled from the Norwegian-Greenland Sea and dated as being between 38 and 30 million years old.
The debris consists of pebbles and mineral grains showing characteristic surface features indicating that they were frozen into glacial ice which subsequently calved as icebergs at the coast. Then, as the icebergs melted, the rock debris was shed into the water column and subsequently incorporated in seafloor sediments. Surface textures and size distributions indicate that the ice-rafted debris was glacial in origin (melted from continental ice) rather than shed from sea ice.
James Eldrett, Ian Harding, Paul Wilson, Emily Butler and Andrew Roberts, all of the University of Southampton's School of Ocean and Earth Science, which is based at NOCS, used ice-rafted debris (IRD) analysis, photographic, electron microscopic, geochemical and rock magnetic techniques in their research which was partially funded by the Natural Environment Research Council.
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Notes for editors
- The National Oceanography Centre, Southampton (NOCS) opened in 1995 in a purpose-built, £50 million waterfront campus on the city's Empress Dock. A joint venture between the University of Southampton and the Natural Environment Research Council, the centre houses around 500 staff and 650 undergraduate and postgraduate students. Ocean-going Royal Research Ships are also based at the centre with a new vessel, RRS James Cook, joining the fleet in March 2007.
- The University of Southampton is a leading UK teaching and research institution with a global reputation for leading-edge research and scholarship. It is one of the UK's top 10 research universities, offering first-rate opportunities and facilities for study and research across a wide range of subjects in humanities, health, science and engineering. The University has around 20,000 students and over 5000 staff. Its annual turnover is in the region of £310 million.