Climate variability during Marine Isotope Stage 11 and the Holocene on the Portuguese Margin
Abstract
Marine Isotope Stage (MIS) 11 and the Holocene are often seen as equal as the orbital parameters and greenhouse gas concentrations during the prominent interglacial 400 ky ago were similar to the ones of the present interglacial period. To study these analogues on the Portuguese Margin we use core MD03-2699 retrieved from the Estremadura Spur north of Lisbon for the MIS 11 record, while the Holocene variations are based on two sediment sequences: 1) MD03-2699 in conjunction with box core PO287-44B from the same location; and 2) core D13882, D13902 and a box cores from the Tagus prodelta off Lisbon, collected at 90m water. Sea Surface Temperatures (SST) reconstructed by the Uk'37 alkenone index suggest that climate conditions during MIS 11 were not significantly different from those registed during the elapsed portion of the Holocene. The SST change at the glacial to interglacial transition (at the transition preceding the interglacials) is characterized by an abrupt rise of 6 degrees C in 1750 yr during for the MIS 11 and 8 degrees C in 280 yr for the transition to the Holocene. The maximum values of Holocene SST, close to 19ºC occur between 10,5 and 9,7 ky BP, while the MIS 11 record reveals two warmer phases: the first with maximum SST close to 18ºC (427 to 412 ky BP) and a second with temperatures close to 19ºC (407 to 395 ky BP). Both periods display a SST decrease following the maximum, which in the case of MIS 11, however, is interrupted by the second SST increase that marks the peak interglacial. Amplitude of SST variation of 1.5 degrees C is similar during both interglacial periods. The results obtained prove that the first part of MIS 11 (427 to 412 ky) and the last 10,5 ky have a similar SST record implying that hydrographic conditions must have been similar during both periods. The maximal SSTs are always associated with the insolation maximum during the respective interglacial, i.e. at the beginning of the Holocene and during MIS 11.3.1.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMPP23C1785R
- Keywords:
-
- 4900 PALEOCEANOGRAPHY (0473;
- 3344);
- 4901 Abrupt/rapid climate change (1605);
- 4936 Interglacial;
- 4954 Sea surface temperature