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Synthesis of Sea Level During the Penultimate Interglacial

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Andrea Dutton

Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia, andrea.dutton@anu.edu.au

 

Over the past decade a number of new sea level archives have greatly enhanced our knowledge of the magnitude and timing of sea level changes during the penultimate interglacial, also known as marine isotope stage (MIS) 7.  Direct markers of sea level position before the last interglacial period are generally rare owing in part to physical overprinting of features during the last interglacial and Holocene highstands in tectonically stable areas.  This physical overprinting is particularly problematic for elucidating evidence of former highstands at similar elevations, such as during MIS 7 which reputedly had at least one, if not more, sea level highstand(s) near present sea level.  In contrast, uplifting coastlines, such as those found at Huon Peninsula or Barbados, may record spectacular geomorphological features (in this case coral terraces) that formed during the penultimate interglacial.  However, reconstructing the elevation of sea level in these tectonically active areas is complicated by assumptions regarding the rate—and uniformity in rate—of uplift.  The magnitude of uncertainty in sea level elevation in uplifting areas therefore increases the further back in time these rates of uplift are extrapolated. 

            In addition to these challenges in determining the elevation of sea level during the penultimate interglacial, the chronology of sea level oscillations during this period of time has been historically hampered by diagenetic alteration of datable material such as fossil corals.  Although the deterioration of coralline aragonite has led to open-system behavior of the U-Th isotope system in most MIS 7 corals that have been studied, a handful of ‘reliable’, high-precision data do exist and modeling of open-system behavior has allowed for a the construction of a significantly richer dataset.  Alternative sources of data have also been sought, and recent contributions from the dating of aragonitic sediments in cores from the Bahamas and of submerged speleothems in Italy have added significant chronological constraints on the timing of sea level highstands during MIS 7. 

            This presentation will focus on providing a synthesis of sea level data across the entirety of MIS 7, highlighting where discrepancies and gaps in the data exist and where significant contributions can be made.  Existing sea level data will also be compared to more continuous models and reconstructions of sea level across this interval to determine which of these reconstructions agrees best with the data—and why.  Finally, some analysis of climatic changes and forcing mechanisms will be included to give a more complete picture of the current state of our understanding of climate dynamics and sea level change during the penultimate interglacial.

Last updated: September 9, 2009
 


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