Details of Award
NERC Reference : NE/D006465/1
Pliocene Intensification of Northern Hemisphere Glaciation: New Constraints from North Atlantic IODP Sediments.
Grant Award
- Principal Investigator:
- Professor PA Wilson, University of Southampton, Sch of Ocean and Earth Science
- Co-Investigator:
- Dr R Schiebel, ,
- Grant held at:
- University of Southampton, Sch of Ocean and Earth Science
- Science Area:
- Earth
- Overall Classification:
- Earth
- ENRIs:
- Global Change
- Science Topics:
- Palaeoenvironments
- Climate & Climate Change
- Abstract:
- One hundred million years ago (Ma), when dinosaurs walked Earth, most scientists believe that the poles were free of the large icecaps that are so familiar to us today. When and why did these icecaps form? How rapidly did they grow? Once established, how stable were they? These are some of the questions that palaeoclimatologists seek to answer using cores of sediment collected from the deep seafloor (which provide the least disturbed record). One of these techniques is to count small rock fragments, ice-rafted debris (IRD) that have been scrapped off the continents by glaciers and delivered to the seafloor by calving and drifting of icebergs. Another is to measure chemical signatures (that are known, from laboratory experiments to be sensitive to ice-volume and temperature) trapped in the fossilised calcium carbonate shells of tiny single cellular marine animals called foraminifera. Application of these techniques to sediment deposits previously available has proved remarkably successful. We now have a semi-continuous, semi-quantitative picture of climate change over the past 100 Ma. The pattern is one of overall gradual (multi-million year scale) long-term cooling plus several more pronounced 'shifts' to more glaciated conditions. Superimposed on these changes are regular cycles in climate with distinct rhythms (eg. ~100, 40 thousand years) and yet more rapid millennial-scale changes. The semi-continuous nature of old palaeoclimate records is steadily being remedied by modern drilling techniques that collect continuous sections of sediment from the seafloor but the semi-quantitative nature of these records has proved a bigger problem. One of the main chemical techniques used for documenting global climate change (the ratio of oxygen-18 to /16 in foraminifera shells, d18O) is sensitive to both changes in temperature and changes in ice-volume (luckily in the same direction), so in the past it has been difficult to separate the two effects. Recently however, the development of a new chemical technique for tracing past changes in temperature independent of ice-volume (by measuring the ratio of Mg to Ca in the shells of foraminifera) has made it possible, through the application of dual d18O and Mg/Ca measurement, to quantify global ice budget. The race is now on to apply this technique to rapidly accumulating sediments with excellent age control. Interestingly, the shift to large permanent ice-sheets occurred much earlier on Antarctica (~30 Ma) than in the northern hemisphere (~3 to 4 Ma). A great deal of debate has arisen as to the cause of this curious sequence of events. Suggested explanations involve changes in ocean circulation patterns, atmospheric CO2 levels, Earth's orbit of the Sun and moisture supply to high latitudes. In a recent study we showed that the development of the first large permanent ice-sheets on Antarctica occurred more rapidly than previously shown, in lock-step with a prominent de-acidification of the ocean during an interval when Earth's orbit of the Sun favoured cool Southern Hemisphere summers. These findings, together with the lack of a major decrease in Mg/Ca and the size of the d18O signature documented (too large to be explained by increased ice-volume alone) point to carbon cycle and orbital-led cooling rather than the hydrological cycle-led moisture supply as the trigger for early maturation of southern hemisphere glaciation. Here propose to apply the same techniques to new cores of rapidly accumulating ocean sediment from the North Atlantic (recovered using modern techniques) understand the later maturation of northern hemisphere glaciation. We will test competing hypotheses of seasonal cooling versus moisture supply as the mechanisms for intensification of northern hemisphere glaciation and (ii) prepare for a more extensive study designed to understand millennial-scale climate change during an interval with ice-sheet boundary conditions relevant to those projected for the future.
- NERC Reference:
- NE/D006465/1
- Grant Stage:
- Completed
- Scheme:
- Directed Pre FEC
- Grant Status:
- Closed
- Programme:
- IODP
This grant award has a total value of £12,000
FDAB - Financial Details (Award breakdown by headings)
| Total - Staff | Total - Other Costs | Total - Indirect Costs |
|---|---|---|
| £6,904 | £1,920 | £3,176 |
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