RT Dissertation/Thesis
T1 Late Quaternary palaeoclimate in the eastern North Atlantic : a multiproxy approach
T2 Paleoclima del Cuaternario superior en el Atlántico Noreste : una aproximación multiproxy
A1 Plaza Morlote, Maider
K1 2502.05 Paleoclimatología
K1 31 Ciencias Agrarias
K1 2507.04 Paleomagnetismo
AB The study of past circum-Atlantic ice sheet motions and instabilities and the reconstrucction of related changes in the strength of the North Atlantic deep bottom-currents is fundamental to understand the effects of past climate changes, and subsequently to predict the effect of future changes. An important part of the reseach efforts produced in this regard have focused on the Lauretide ice-sheet (LIS), leaving the potential role of the European Ice Sheet (EIS) relatively unexplored. Similarly, the millennial changes in the bottom-currents strength, their potential relationship to the Atlantic Meridional Overturning Circulation (AMOC) variations and the deep and intermediate water masses re-accommodations remains also very weakly constrained. The main objective of this thesis is to study the interrelated dynamics of the Northern Hemisphere ice sheets during the Last Glacial Period (LGP) and their coupling with the Thermohaline circulation,( THC), AMOC and the climate, focussing on the time period of the last ~80 ka, during which the North Hemisphere climate and the ice-sheets volumes fluctuated rapidly. The study is based on high-resolution sedimentological, geochemical and environmagnetic analyses of the sedimentary record of the last 135 ka based on five well-dated piston cores from the Galicia Interior Basin in the Northwest Iberian Margin. The results show the southernmost evidence of meltwater pre-events from the EIS during the initial stages of HS1, HS2, and HS4, and IRD from the LIS and EIS during the final stages of these stadials, and throughout HS3, HS5 and HS6. The relevance of this findings reside in the potencial for large freshwater discharges like these, to act as an additional forcing mechanism for AMOC weakening; and subsequently, for ice sheets collapses, prolonging the Heinrich Stadials. The results also show the intensification of bottom current velocities during HS3, HS5, HS6, the Last Glacial Maximum, and through the final stages of the HS1, HS2 and HS4. However, these increases in the vigor of the North Atlantic Water mass (NADW), under which is currently submitted our record, have not been reported in other North Atlantic regions during these time intervals, but there are decreases in their vigor. Thus, such increases in the velocity of the bottom-currents are most likely driven by the Mediterranean Outflow Water (MOW). The intensification and deepening of the MOW during these cold phases, described in the southern sector of the Iberian Continental Margin, could have reached the latitudes and depths of the study area due to the hydrographic reorganizations known to have occurred during HSs and MIS II. This supports the hypothesis of MOW’s salt injection into the intermediate North Atlantic waters preconditioning the MOC to switch from the stadial to the interstadial mode.
YR 2018
FD 2018-03-12
LK http://hdl.handle.net/11093/961
UL http://hdl.handle.net/11093/961
LA eng
NO Ministerio de Economía y Competitividad de España (CGL2010-16688)
DS Investigo
RD 22-sep-2023