Phase relationship between sea level and abrupt climate change

Abstract

Direct traces of past sea levels are based on the elevation of old coral reefs at times of sea-level highstands. However, these measurements are discontinuous and cannot be easily correlated with climate records from ice cores. In this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged, even during periods of sea-level lowstand. By using a sediment core precisely synchronized with Greenland ice cores, we were able to recognize major floods of the Mediterranean continental shelf over the past 270 kyr. During the last glacial period five flooding events were observed at the onset of the warmest Greenland interstadials.Consistent correspondence between warm climate episodes and eustatic sea level rises shows that these global flooding events were generated by pronounced melting of the 2 Northern Hemisphere ice-sheets, due to rapid intensification of Atlantic Meridional Overturning Circulation.The method described in this study opens a new perspective for inter hemispheric synchronization of marine climate records if applied in other continental margins from the Southern Hemisphere or the equatorial regions.

A 500 kyr record of global sea-level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea-level variability

“…The sedimentary units end with an abrupt increase in the silt/clay ratio and a rapid decrease in the Ca content coinciding with the main reflectors corresponding to sequence boundaries in the seismic reflection profile. The excellent correlation of these analytical sequences with the seismostratigraphy, together with chronostratigraphic control from the G. bulloides δ 18 O record (Sierro et al, 2009) confirm the 100-kyr-cycle origin of these units. The data derived from PRGL1-4 borehole allowed us to reinterpret the seismostratigraphy of the GoL upper slope, where seven units (S1, S2a, S2b, S3a, S3b, S4 and S5) are now documented (Jouet, 2007), instead of the five (S1 to S5) previously identified from seismic reflection profiles alone (Rabineau, 2001).…”

“…3), with the support of the planktic oxygen isotope records from the Portuguese margin (Roucoux et al, 2006) and the North Atlantic region (Stein et al, 2009) for specific time intervals. For more details on the age model, tie points and 14 C-AMS dates see Sierro et al (2009). Work is in progress to further improve time constrains during MIS 12 and 13 (F. J.…”

“…(B) LR04 benthic isotope stack record used as reference record (Lisiecki and Raymo, 2005). PRGL1-4 records of (C) G. bulloides δ 18 O, (D) Ca-free silt/clay ratio, (E) total fine sand (%) (Sierro et al, 2009), (F) XRF-Ca, and (G) linear sedimentation rates. The top 22 ka of the G. bulloides δ 18 O record (purple), the silt/clay ratio of the carbonate-free fraction (blue) and the total fine sand (pink) are from overlapping core MD99-2348, which include the abrupt change associated with the last deglaciation that is not covered by the XRF-Ca record of PRGL1-4.…”

“…addition, the very low SRs during the main interglacial highstands led to the formation of condensed layers (CLs), i.e., sandy layers rich in pelagic skeletal material, along the GoL upper slope (Fig. 3e), as shown by the total (bulk fraction, non carbonate-free) fine sand record of Sierro et al (2009) (Fig. 3e).…”

“…In fact, MIS 3 relative sea-level rises have been tentatively associated with both contributions from the Antarctic and the Laurentide ice sheets (Arz et al, 2007;Rohling et al, 2008;Siddall et al, 2003Siddall et al, , 2008Sierro et al, 2009), thus, evidencing the lack of consensus on the sea-level response to rapid climate variability.…”