• Energy Research

Down‐core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in International Marine Past Global Changes Study (IMAGES) core MD99‐2343 in order to study the interactions between climate change in the Northern Hemisphere and the western Mediterranean thermohaline circulation at times of Heinrich events (HE). Our results confirm the antiphase correlation between enhanced North Atlantic Deep Water formation and low ventilation in the Mediterranean. However, this study reveals that this antiphase relationship in deepwater formation between the North Atlantic and Mediterranean was interrupted during times of HE when the injection of large volumes of water from melting icebergs reached the entrance to the Mediterranean. These events, which lasted less than 1000 years, are represented by pronounced decreases in both planktonic δ18O and benthic δ13C signals. Lower salinities of Mediterranean surface water resulted in a slowdown of western Mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation.

A continuous high-resolution Western Mediterranean sea surface temperature (SST) alkenone record spanning the past 250,000 years shows that abrupt changes were more common at warming than at cooling. During marine isotope stage (MIS) 6, SST oscillated following a stadial-interstadial pattern but at lower intensities and rates of change than in the Dansgaard/Oeschger events of MIS 3. Some of the most prominent events occurred over MISs 5 and 7, after prolonged warm periods of high stability. Climate during the whole period was predominantly maintained in interglacial-interstadial conditions, whereas the duration of stadials was much shorter. Supplement to: Martrat, Belén; Grimalt, Joan O; López-Martinez, Constancia; Cacho, Isabel; Sierro, Francisco Javier; Flores, José-Abel; Zahn, Rainer; Canals, Miquel; Curtis, Jason H; Hodell, David A (2004): Abrupt Temperature Changes in the Western Mediterranean over the Past 250,000 Years. Science, 306(5702), 1762-1765

AbstractPlanktonic Foraminifera are unique paleo-environmental indicators through their excellent fossil record in ocean sediments. Their distribution and diversity are affected by different environmental factors including anthropogenically forced ocean and climate change. Until now, historical changes in their distribution have not been fully assessed at the global scale. Here we present the FORCIS (Foraminifera Response to Climatic Stress) database on foraminiferal species diversity and distribution in the global ocean from 1910 until 2018 including published and unpublished data. The FORCIS database includes data collected using plankton tows, continuous plankton recorder, sediment traps and plankton pump, and contains ~22,000, ~157,000, ~9,000, ~400 subsamples, respectively (one single plankton aliquot collected within a depth range, time interval, size fraction range, at a single location) from each category. Our database provides a perspective of the distribution patterns of planktonic Foraminifera in the global ocean on large spatial (regional to basin scale, and at the vertical scale), and temporal (seasonal to interdecadal) scales over the past century.

A continuous high-resolution Western Mediterranean sea surface temperature (SST) alkenone record spanning the past 250,000 years shows that abrupt changes were more common at warming than at cooling. During marine isotope stage (MIS) 6, SST oscillated following a stadial-interstadial pattern but at lower intensities and rates of change than in the Dansgaard/Oeschger events of MIS 3. Some of the most prominent events occurred over MISs 5 and 7, after prolonged warm periods of high stability. Climate during the whole period was predominantly maintained in interglacial-interstadial conditions, whereas the duration of stadials was much shorter.

This article is subject to a Creative Commons Attribution Non-Commercial No Derivatives License The Pliocene is a key period in Earth's climate evolution, as it records the transition from warm and stable conditions to the colder and more variable glaciated climate of the Pleistocene. Simultaneously, climate became more seasonal in the Mediterranean area, and Mediterranean-type seasonal precipitation rhythm with summer drought established. These climatic changes presumably had significant impacts on terrestrial environments. However, the response of terrestrial environments to such climate changes is still not fully understood due to the lack of detailed studies dealing with this period of time. In this study, multiproxy analyses of continuous core sampling from La Matilla (SW Spain) shows detailed and continuous record of pollen, sand content and abundance of benthic foraminifer Bolivina spathulata to describe paleoenvironmental and paleoclimate trends during the early Pliocene. This record shows warmest, most humid climate conditions and highest riverine nutrient supply at ~ 4.35 Ma, coinciding with the Pliocene climatic optimum and high global sea level. A climate cooling and aridity trend occurred subsequently and a significant glaciation occurred at ~ 4.1–4.0 Ma, during a period known by very little terrestrial evidence of glaciation. Our multiproxy data thus indicate that terrestrial and marine environments were significantly variable during the early Pliocene and that major glaciation-like cooling occurred before the intensification of northern hemisphere glaciation at the beginning of the Pleistocene (~2.7 Ma). This major climate cooling and aridity maxima between 4.1 and 4.0 Ma is independently validated by a coeval sea-level drop (third order Za2 sequence boundary). This sea level drawdown is supported by enhanced coarse sedimentation and minima in riverine nutrient supply, showing paired vegetation and sea-level changes and thus a strong land-ocean relationship. This study also shows that long-term climatic trends were interrupted by orbital-scale cyclic climatic variability, with eccentricity, obliquity and precession acting as the main triggers controlling climate and environmental change in the area. © 2019 Elsevier B.V. This study was supported by the research projects CGL2012-30875 (GUADALTYC), CGL2013-47038-R, CGL-2017-85415-R and CGL2014-59516 (MITE) of the Ministerio de Economía y Competitividad of Spain, project P11-RNM-7332 from the Junta de Andalucía, and the Research Groups RNM-190 of the Junta de Andalucía and GRC Geociències Marines (2017 SGR 315) of the Generalitat de Catalunya. Peer reviewed