T55 Rapid Sea-Level Rise and Its Impacts: Past, Present, and Future II
Sunday, 4 November 2012
1:30 PM - 5:30 PM
219AB
MISSISSIPPI DELTA MARSH TIPPING POINTS LINKED TO A HOLOCENE RELATIVE SEA-LEVEL RECORD: IMPLICATIONS FOR FUTURE COASTAL MARSH SUSTAINABILITY
Paper number: T55-11
Program: Technical Sessions
Time: 4:10 PM – 4:25 PM
Authors
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Yongxiang LiNanjing University, Nanjing, N/A
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Torbjörn E. TornqvistTulane University, New Orleans, LA
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Barry KohlTulane University, New Orleans, LA
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Jennifer I. KuykendallTulane University, New Orleans, LA
Abstract
Coastal wetlands provide Louisiana with abundant ecosystem services, including protection from coastal hazards. Sea level is projected to rise by as much as 1 m in the coming century due to anthropogenic climate change. Short-term (< 10 years) coastal marsh sustainability studies suggest rates of marsh surface elevation gain of ~1 cm/yr, which would enable marshes to keep pace with projected rates of sea-level rise. However, it remains unknown what the sustainability of these ecosystems is in the longer term. Here we investigate the multi-decadal to century scale marsh response to varying rates of relative sea-level rise over the past 8500 years through a detailed stratigraphic analysis in association with 72 sea-level index points from the Mississippi Delta. Our preliminary results identify two marsh sustainability tipping points. At sea-level rise rates > 8 mm/yr, marshes drown almost instantaneously (i.e., within a few decades) and are entirely unsustainable. However, even at rates as low as ~3 mm/yr, marshes eventually drown and are converted into shallow lagoons over century timescales. We suggest that the long-term compaction effect on marsh response to sea-level rise may not be captured in short-term marsh sustainability studies, resulting in too optimistic assessments of marsh resiliency.