By Kelly

Photograph by Dan Zwartz
Photograph by Dan Zwartz

ANU researchers (past and present) reveal that in my youth, during the last interglacial 125,000 years ago, sea level was many metres higher than previous models have predicted. In an article published in  Science yesterday, new evidence reveals that during this period in Earth’s history sea-level was likely 5.5-9 meteres higher than present. The last interglacial is of particular interest to climate scientists as it is the closest analogue (or comparison) to present day climate.

“For the period we studied, the poles were probably only 3 to 5 degrees warmer than present.  That amount of polar warming is well within what we are predicted to reach this century. This implies that the polar ice sheets may be very sensitive to small increases in temperature” said Andrea Dutton, lead author and former RSES researcher in a statement released by the ANU media office. To achieve this amount of sea-level change, the geophysical model they propose required part of the Greenland ice sheet, most of the West Antarctic ice sheet, and possibly even some of the East Antarctic ice sheet to melt.

“Given the modest difference in temperature between our present climate and that of the last interglacial period, it is time to start thinking about the legacy we will leave for future generations with the choices we make today.”

In this study, historical sea level was reconstructed from a geophysical model based on our understanding of how the earth deforms under the weight of ice sheets and stratigraphic evidence found in fossil corals.  Corals (or more specifically their symbionts) require sunlight to grow, and  therefore habit surface waters. The team were able to age fossil corals, using uranium-series dating, to investigate past sea surface and model the volume of ice cap melt that would be required to cause such change. Modelling sea-level change  is complicated due to global variation in the way the solid earth deforms in response to ice sheet and water loads both, at the time of the event and during preceding glacial periods and the over print of more regional tectonic activity. Andrea Dutton and Kurt Lambeck, formerly and currently of RSES respectively, report observations from 16 sites around the globe, 6 of which are considered tectonically stable, to recalculate sea-level during a period in Earth’s history with temperatures similar to what we are experiencing today.

“This magnitude of sea level rise – up to 9 metres – is obviously not going to happen overnight. But it could happen within a few centuries, so it is important to consider the long-term commitment we make in terms of total sea level rise when we talk about various targets and emission scenarios.”

Andrea was an absolute inspiration to many of us during her time at RSES, and continues to be one, even from her far-field position, at the University of Florida.

The full article can be found here and the ANU media release here.