A new Holocene sea-level database for the US Gulf Coast: Improving constraints for past and future sea levels
Abstract
The interpretation of present-day sea-level change, as well as the prediction of future relative sea-level (RSL) rise and its spatial variability, depend increasingly on the ability of glacial isostatic adjustment (GIA) models to reveal non-eustatic components of RSL change. GIA results from the redistribution of mass due to the growth and decay of ice sheets. As a consequence, formerly ice-covered areas are still rebounding and currently experience RSL fall, while in other areas the rate of RSL rise is enhanced due to glacial forebulge collapse. The development of GIA models relies to a large extent on the availability of quality-controlled Holocene RSL data. There is thus an urgent need for systematically compiled and publicly available databases of geological RSL data that can be used not only for the purposes mentioned above, but also can serve to underpin coastal management and policy decisions. We have focused our efforts to develop a Holocene sea-level database for the Atlantic and Gulf coasts of the US. Many of the research problems that can be addressed with this sea-level database revolve around the identification of crustal motions due to glacial forebulge collapse that affects the entire region and likely extends beyond South Florida. For the east coast, GIA-related subsidence rates have been calculated with unprecedented precision: <0.8 mm a-1 in Maine, increasing to rates of 1.7 mm a-1 in Delaware, and a return to rates <0.9 mm a-1 in the Carolinas. Here, we first define our methodology to reconstruct RSL, with particular reference to the quantification of age and elevation errors. Many sea-level indicators are related to a specific tide level (e.g., peat that formed between highest astronomical tide and mean high water level). We use paleotidal modeling to account for any changes during the Holocene. We furthermore highlight a number of errors associated with 14C dating that have rarely, if ever, been considered in previous studies of this nature. Second, we show the spatially variable RSL history along the US Gulf Coast. The rates of RSL rise reflect differential GIA, augmented in the Mississippi Delta region by enhanced rates of subsidence due to sediment loading. Similar to our conclusions from the Atlantic coast, the Holocene database constrains rates of vertical land movement, either caused by GIA or sediment loading, significantly better than currently available geodetic data.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMGC54B..04H
- Keywords:
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- 1105 GEOCHRONOLOGY / Quaternary geochronology;
- 1223 GEODESY AND GRAVITY / Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions;
- 1641 GLOBAL CHANGE / Sea level change