Continental ice in Greenland during the Eocene and Oligocene

Abstract

The Eocene and Oligocene epochs (approximately 55 to 23 million years ago) comprise a critical phase in Earth history. An array of geological records supported by climate modelling indicates a profound shift in global climate during this interval, from a state that was largely free of polar ice caps to one in which ice sheets on Antarctica approached their modern size. However, the early glaciation history of the Northern Hemisphere is a subject of controversy. Here we report stratigraphically extensive ice-rafted debris, including macroscopic dropstones, in late Eocene to early Oligocene sediments from the Norwegian-Greenland Sea that were deposited between about 38 and 30 million years ago. Our data indicate sediment rafting by glacial ice, rather than sea ice, and point to East Greenland as the likely source. Records of this type from one site alone cannot be used to determine the extent of ice involved. However, our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.

Expanding the Cenozoic paleoceanographic record in the Central Arctic Ocean: IODP Expedition 302 Synthesis

“…The question about the timing of Northern Hemisphere cooling and bipolar ice sheet formation has been much debated in recent years [94][95][96][97][98]. In a study of the ACEX coarse fraction, St. John [100] confirmed the initial interpretation of early occurrence of IRD in the ACEX record [19,41] (Figure 5).…”

New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling

“…Site 913 drilled during Leg 151 (Fig. 1) contains macroscopic drop-stones within a section of extensive ice-rafted debris (IRD) dated to the late Eocene to early Oligocene (38e30 Ma) (Eldrett et al, 2007). The authors interpreted this increase in IRD and occurrence of dropstones to indicate the existence of, at the minimum, isolated glaciers on East Greenland that were calving icebergs into the North Atlantic.…”

Recent advances in understanding Antarctic climate evolution

“…Furthermore new isotopic analyses of deep sea sediments of Eocene age are now being taken to imply periods of significant ice cover in both Polar Regions (Tripati et al 2005). These observations suggest that either our interpretations of the proxy data are faulty, or episodic, bipolar glaciation occurred much earlier than currently accepted (Eldrett et al 2007). These, among other unresolved controversies related to the climatic and glacial evolution of the high southern latitudes will be the focus of future modelling and model-data comparisons.…”