Far out in North Carolina

The day I arrived on the Outer Banks I’d been greeted with news of a 50:50 chance of a tropical storm developing offshore. The same evening the first tropical storm of the season was called by the National Hurricane Center: Alberto. In mid-May – the hurricane season officially only starts in June (it turned out to be only the third May on record with two tropical storms in the Atlantic). The Outer Banks are very exposed. Several times in the last decades a hurricane caused a break in the barrier island and washed away the only road connection to the mainland. Luckily, Alberto turned offshore and passed far out at sea without bothering us.

Andy Kemp (on right) with students Ray and Hanna.

We’re here because of the several metres thick peat layer which has accumulated during the past millennia behind the Outer Banks. The land here is still sinking since the end of the last Ice Age, because it is located on the glacial forebulge: a zone around the edges of the glacial ice sheets that was pushed up when the ice load was pushing down adjacent lands. So instead of getting post-glacial uplift it suffers from post-glacial subsidence. The subsidence has led to a continuous sea-level rise relative to the land of around one millimetre per year. The salt marsh is able to keep up with this rise by accumulating sediments and building up peat, about a metre per millennium. This provides a unique opportunity to reconstruct the speed of relative sea-level rise – and by subtracting out the land subsidence, also the absolute sea-level changes.

I’ve already reported here on the previous results of our collaboration with the team around Ben Horton of the University of Pennsilvania: it was possible to reconstruct sea level for the past 2,000 years and to link the variations of the last 1,000 years to the global temperature evolution (see graph in that earlier post). Now we’re here to look for even older, thicker peat. Some of the oldest peat may well have been flooded in the meantime and be sitting at the bottom of the lagoon, hence we’re also coring from aboard the research vessel run by East Carolina University. After more than a week of coring, the peat is looking promising – but only months-long efforts in the lab will show whether the new cores are suitable for reconstructing sea level.

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