Rapid warming at the end of the last Eemian interglacial caused sea level to rise several meters – just before ice age returned

This palaeo climate reconstruction of the interglacial before our own Holocene – the one called the Eemian – obtained identical results in the Caribbean and in Australia showing a remarkable warming peak at the very end of that interglacial.

Link (remove spaces): http : //350.me.uk/TR/Hansen/GlobalSeauow045009 . pdf

Even more strikingly, this warming was accompanied by as much as 9 meters of ocean level rise.

We know now, of course, that it was just before the end of the interglacial and a sharp drop to frigid glacial conditions.

But those living then would not have known that. They would simply be experiencing global warming. They were probably thinking – did we cause this? How much warmer is it going to get?

Studies such as this one by Hearty et al 2007 suggest that a brief anomalous warming spike is a common feature of the end of interglacials, happening just before glacial inception and a sharp cooling as the next”ice age” returns.

This puts our current century of climate warming in an interesting perspective.

As the authors say, it “provides one ominous scenario for a greenhouse world.”

Citation:

Hearty, P. J., Hollin, J. T., Neumann, A. C., O’Leary, M. J., & McCulloch, M. (2007). Global sea-level fluctuations during the Last Interglaciation (MIS 5e). Quaternary Science Reviews26(17-18), 2090-2112.

Abstract:

Global sea-level fluctuations during the Last Interglaciation (MIS 5e)

Paul J. Hearty(a), John T. Hollin (b), A. Conrad Neumann )c), Michael J. O’Leary (d), Malcolm McCulloch (e) 

(a) School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia 

(b) Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA

(c) Marine Sciences Department, University of North Carolina, Chapel Hill, NC 27599-3300, USA

(d) Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Manchester M1 5GD, UK

(e) Research School of Earth Sciences, The Australian University, Canberra, ACT 0000, Australia

Received 7 September 2006; received in revised form 11 May 2007; accepted 17 June 2007

The geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the Last Interglaciation (Marine Isotope Stage (MIS) 5e, assumed average duration between 13072 and 11972 ka). Because sea level was higher than present, deposits are emergent, exposed, and widespread on many stable coastlines. Correlation with MIS 5e is facilitated by similar morphostratigraphic relationships, a low degree of diagenesis, uranium–thorium (U/Th) ages, and a global set of amino-acid racemization (AAR) data. This study integrates information from a large number of sites from tectonically stable areas including Bermuda, Bahamas, and Western Australia, and some that have experienced minor uplift (􏰁2.5 m/100 ka), including selected sites from the Mediterranean and Hawaii. Significant fluctuations during the highstand are evident at many MIS 5e sites, revealed from morphological, stratigraphic, and sedimentological evidence. Rounded and flat-topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story. Despite predictions of much different sea-level histories in Bermuda, the Bahamas, and Western Australia due to glacio- and hydro-isostatic effects, the rocks from these sites reveal a nearly identical record during the Last Interglaciation.

The Last Interglacial highstand is characterized by several defined sea-level intervals (SLIs) that include: (SLI#1) post-glacial (MIS 6/5e Termination II) rise to above present before 130 ka; (SLI#2) stability at +2 to +3 m for the initial several thousand years (􏰁130 to 􏰁125 ka) during which fringing reefs were established and terrace morphology was imprinted along the coastlines; (SLI#3) a brief fall to near or below present around 125 ka; (SLI#4) a secondary rise to and through 􏰁+3–4 m (􏰁124 to 􏰁122 ka); followed by (SLI#5) a brief period of instability (􏰁120 ka) characterized by a rapid rise to between +6 to +9 m during which multiple notches and benches were developed; and (SLI#6) an apparently rapid descent of sea level into MIS 5d after 119 ka. U/Th ages are used to confirm the Last Interglacial age of the deposits, but unfortunately, in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages.

Sea levels above or at present were relatively stable during much of early MIS 5e and the last 6–7ka of MIS 1, encouraging a comparison between them. The geological evidence suggests that significant oceanographic and climatic changes occurred thereafter, midway through, and continuing through the end of MIS 5e. Fluctuating sea levels and a catastrophic termination of MIS 5e are linked to the instability of grounded and marine-based ice sheets, with the Greenland (GIS) and West Antarctic (WAIS) ice sheets being the most likely contributors. Late MIS 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts, and provide one ominous scenario for a greenhouse world.

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