Abreu, Lúcia de

Salgueiro, Emília

Voelker, Antje H. L.

Laboratório Nacional de Energia e Geologia Repository

Hydrographic changes along the western Iberian margin : the need to reconstruct and understand regional climate responses for glacial climate record  integration

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Geophysical Research AbstractsVol. 12, EGU2010-12675, 2010EGU General Assembly 2010© Author(s) 2010Hydrographic changes along the western Iberian margin: The need toreconstruct and understand regional climate responses for glacial climaterecord integrationAntje Voelker (1,2), Emilia Salgueiro (1,2), and Lucia de Abreu (3)(1) CIMAR Associated Laboratory, Rua dos Bragas, 289; 4050-123 Porto, Portugal (avoelker@softhome.net), (2) UnidadeGeologia Marinha, LNEG, Estrada da Portela, Zambujal, 2610-143 Amadora, Portugal, (3) Camberley, UK(luciaabreu@yahoo.com)The western Iberian margin is a key region for studying glacial abrupt climate change events because its surfacewater signals reflect oxygen isotope and temperature variations recorded in the Greenland ice core records whileits deep water – below 3000 m – changes follow the Antarctic ice core climate curves (e.g., Shackleton et al., 2000;Paleoceanogr.) allowing for interhemispheric comparisons. In addition, the southern edge of the North Atlantic’sice-rafted debris (IRD) belt, the so called Ruddiman belt, intercepts with the margin. During major ice-raftingevents, i.e. the Heinrich events, this southern limit is associated with the Polar Front (e.g., Eynaud et al., 2009,GCubed).Here we present planktonic stable isotope, IRD, % N. pachyderma (s), and sea surface temperature recordscovering the last 50 ka for a latitudinal core transect along the western Iberian margin. The transect spans fromcore SU92-03 at 43°N via core MD95-2040 at 40.5°N and cores MD95-2042, -2041 and MD01-2444 at 38°N tocore MD99-2339 at 36°N in the central Gulf of Cadiz. By combining the records of these cores we are able toestablish gradients in intensity and duration – assuming that our age models are correct – of the millennial-scaleclimate variability typical for Marine Isotope Stage 3. The data clearly reveals that a boundary, most likelylinked to the southern limit of the IRD belt, existed at about 39°N (Salgueiro et al., in press; QSR). North ofthis boundary cooling/ ice-rafting events had a stronger impact than south of it with % N. pachyderma (s) levelsduring most Heinrich event exceeding 80%, while off Sines at 38°N only 55% are reached during Heinrich event4 and in the central Gulf of Cadiz just 16%. This reduction in % N. pachyderma (s) clearly highlights the reducedimpact of the Polar Front and the associated subpolar waters the further south a site is located. From the northernsites, core MD95-2040 has the higher resolution and its records show that each cooling event – Heinrich eventsand Greenland stadials (GS) – led to significant cooling including IRD deposition. In comparison to the southernsites, especially to MD99-2339 at 36°N, cooling episodes lasted longer, mainly because cooling started earlier inthe north, in agreement with the Polar Front reaching this region first. Comparison between cores MD01-2444(38°N) and MD99-2339 (36°N) reveals that for most of MIS 3 their temperature evolution was similar, includingno cooling associated with GS 11. However, impacts of some events differed between the sites. Thus GS 12 led to>5°C cooling at the Sines site, but had no impact in the central Gulf of Cadiz and GS 10, 9, and 7 and to a lesserextend also Heinrich event 4 had a stronger temperature response at 38°N than at 36°N.The differences in the climatic response along our core transects clearly reveal that on the western Iberianmargin – and in other regions where positions of atmospheric and hydrographic fronts varied strongly with theabrupt climate change events – more than one site is needed to understand the full spectrum of the climate changeand to potentially trace response delays because these delays will play an important role in integrating marinerecords not just between themselves but also with ice core and terrestrial records.

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Hydrographic changes along the western Iberian margin : the need to reconstruct and understand regional climate responses for glacial climate record integration

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