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Science
Interglacials are periods of warmer climates with reduced ice-sheet volume, and those of the past 500,000 years represent a considerable range of different combinations of ice-volume, temperature, sea-level, insolation, and greenhouse-gas concentrations. They provide a unique real-world testing suite for examining how ice-sheet volume and sea level respond to different climate states.

iGlass Projects:

1. Acquisition of new relative sea level data:

Our research focus on several archives of past sea level changes. These are sediments and microfossils (diatoms and foraminifera) from estuarine environments, speleothems (cave deposits), corals and chemical composition of marine plankton shells (foraminifera) contained in sediment cores. We are currently working on material from the UK, Bermuda, Sardinia and the Red Sea.

new data

2. Isostatic modelling:

We are compiling a global synthesis of available data on interglacial sea level changes (if you wish to contribute data, please contact us!). In addition, we will use Glacio-Isostatic Adjustment (GIA) modelling to investigate further the sea level changes during the last glacial cycle, interglacial variability and the contributions from various past ice sheets.

3. Palaeodata synthesis and modelling of climate-ice sheet interactions:

Our research focuses on pdatakey climate parameters over the polar ice sheets and around the ice margins during the last five interglacials (Marine Isotope Stage (MIS) 1, 5e, 7, 9 and 11).

We use archives of past climatic change such as polar ice cores and marine sediments and the proxy records they contain (e.g. the composition of trapped gas bubbles in ice cores or the stable isotope ratios of foraminifera).

In tandem, we are using modelling experiments to investigate climate during the last five interglacials and the configurations of past Greenland and Antarctic Ice Sheets.

 

4. Synthesis and modelling of future sea level change:

From studying of interglacials we will determine:

  1. what aspect of climate forcing allowed ice-volume/sea-level to be so highly variable during interglacials.
  2. the response of the of ice-volume/sea level to different climate states during the past five interglacials.
  3. the potential for a reduction in the Greenland and Antarctic Ice Sheets and contribution to global sea levels in the future.

Addressing such issues is especially pertinent because modelling results (Pollard and DeConto, 2009) suggest that conditions during the Late Quaternary have been critically poised for the development of ‘super-interglacials’, when sea-level could abruptly rise above its present position due to a catastrophic reduction of the West Antarctic Ice Sheet. The highly non-uniform redistribution of water in the world’s oceans, due to gravitational or crustal rebound changes, means that N.E. USA and N.W. Europe are especially vulnerable to sea-level rise driven by Antarctic ice loss, whereas the southern hemisphere would be more at risk from Greenland melting (Mitrovica et al., 2001).

Although significant progress has been made in reconstructing sea-level changes during past interglacials, this work has also revealed considerable discrepancies between reconstructions from different techniques and study regions. In addition, it has proven challenging to advance our understanding of ice-sheet models to a point at which realistic simulation of ice sheets as a function of climate becomes possible. This is largely because existing work relies on only one climate state (the most recent conditions) or at most one further interglacial (the Last Interglacial). When considering only one climate state, a relatively large set of model configurations can reasonably simulate the ice sheets. By introducing sequentially more climate states in models that are tested and validated for the current interglacial, these degrees of freedom become increasingly limited, which reduces the potential suite of model configurations that can reasonably simulate ice-sheet behaviour as a function of climate.

iGlass will develop a sound understanding of the sensitivity of ice-sheet volume to different interglacial climate states. Only a broad-ranging interdisciplinary project that integrates field data and modelling can establish whether (and from where) large ice-volume reductions relative to the present have happened, and then identify the set of ice-sheet model configurations that reasonably simulate the ice sheets given the current knowledge of the prevailing climate states. This requires a well-integrated, coordinated consortium of experts from a variety of disciplines, spanning sealevel and climate reconstructions to isostatic and ice-sheet/climate modelling. Such an approach lays the critical foundations to a process-led understanding of the future ice-sheet contribution to sea-level changes, and hence to develop defined limits to improved H++ sea-level scenarios.

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