Warm climate, high seas. How did sea level change in Europe during the Last Interglacial?

The big picture
Global sea-level rise is one of our greatest environmental challenges and is predicted to continue for hundreds of years, even if global greenhouse-gas emissions are stopped immediately (Clark et al., 2016). However, the range, rates and responses to sea-level rise beyond 2100 are poorly understood. Current models that project sea-level rise centuries into the future have large uncertainties, because the recent observations upon which they are based encompass too limited a range of climate variability. Therefore, it is crucial to turn to the geological record where there are large-scale changes in climate. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at the poles (a pattern similar to that predicted in the coming centuries), and global sea level was 6-9 m higher (Dutton et al., 2015), far above that experienced in human memory.

The PhD project
This PhD project forms part of the €2 million European Research Council Starting Grant, “Rates of Interglacial Sea-Level Change and Responses” (RISeR) which aims to advance our understanding of the magnitude, rates and drivers of sea-level change during the Last Interglacial, to inform both global and regional sea-level projections beyond 2100.

RISeR is focusing on developing a state-of-the-art Last Interglacial sea level record from northwest Europe. Relative sea-level changes in northwest Europe are a consequence of change in the volume and distribution of water in the global ocean, but also solid earth processes as a result of regional loading by ice sheets during glacial periods (termed glacial isostatic adjustment, GIA). This PhD project will develop a regional GIA model to understand the solid earth response in northwest Europe during the Last Interglacial. The student will use a new generation of ice-sheet models within a global GIA model to compare to and interpret the new Last Interglacial relative sea-level reconstructions produced by the wider RISeR project. This work will provide the first regional Last Interglacial glacial-isostatic adjustment model and a statistical assessment of the likelihood of different melt water sources to the Last Interglacial highstand and their contribution to relative sea-level change in northwest Europe.

The methods
Research into Last Interglacial global datasets has shown the importance of the inputted ice sheet history with the need to better constrain its spatially variable distribution, rather than simply scaling for total ice-volume changes based upon the marine oxygen-isotope curve (Dendy et al., 2017; Rohling et al., 2017). Last Interglacial GIA research to-date has been on a global scale, which provides an excellent framework for PhD project to look at regional GIA in northwest Europe in detail. Regional case-studies have been a critical part of constraining post LGM and Holocene GIA models and this PhD will contribute to the next-generation of Last Interglacial GIA models, which have been identified as crucial to be able to better understand the rates and magnitudes of Last Interglacial sea-level change (Rohling et al., 2017). Understanding Last Interglacial solid earth processes, is also an important part of being able to use the Last Interglacial as an analogue for future coastal response to rates of RSL change under a warm climate, as the pattern of GIA during the Last Interglacial and the next centuries will differ.

The GIA modelling will conducted using a gravitationally self-consistent global sea-level model with Earth rotational feedbacks, migrating shorelines and deformation of a viscoelastic Earth with radially varying Earth structure, which has been used to answer a range of sea-level problems (Gomez et al., 2015a; Gomez et al., 2015b; Gomez et al., 2013; Hay et al., 2014). By subtracting the modelled GIA driven regional land-level changes from the reconstructed RSL curve, it will be possible derive an estimate of the contribution to the rates of change from ice loss during the interglacial period. This will be used to ‘fingerprint’ the sea-level signal for Last Interglacial ice loss (Greenland v Antarctica).

A full description can be found at: www.natashabarlow.co.uk including reference list.