Els corrents marins del sud d'Àfrica podrien estabilitzar el clima a Europa

Un consorci internacional de científics marins, del qual forma part Rainer Zahn, professor ICREA del Departament de Física de la UAB i investigador de l'Institut de Ciència i Tecnologia Ambientals (ICTA), està estudiant l'efecte de l'aportació d'aigües salades del Corrent d'Agulhas a l'Atlàntic en condicions d'escalfament global. La recerca, publicada a Nature, suposa un enfocament alternatiu en relació als futurs sistemes de corrents en l'Atlàntic Nord i la seva influència en el clima europeu.Un consorcio internacional de científicos marinos, del que forma parte Rainer Zahn, profesor ICREA del Departamento de Física de la UAB e investigador del Instituto de Ciencia y Tecnología Ambientales (ICTA), está estudiando el efecto del aporte de aguas saladas de la Corriente deAgulhas al Atlántico en condiciones de calentamiento global. La investigación, publicada en Nature, supone un enfoque alternativo en relación a los futuros sistemas de corrientes en el Atlántico NorteAn international team of marine scientists studies the effects salt water from the Agulhas Current can have on global warming. The research, published in Nature, presents an alternative perspective on the future of ocean current developments in the North Atlantic. The study included the participation of Rainer Zahn, ICREA research professor of the Department of Physics at the UAB and investigator at the Institute of Environmental Science and Technology (ICTA)

Els sediments d'oceans mostren claus sobre futurs canvis climàtics

A l'última glaciació, abans que comencessin a desfer-se grans masses de gel dels continents i s'aboquessin a l'Oceà Àrtic, uns primers episodis esporàdics de desgel a l'antic mantell de gel que cobria les Illes Britàniques ja van afectar la circulació dels corrents oceànics, que juguen un paper clau en l'estabilitat climàtica del planeta. Aquest fet suggereix que l'escalfament i l'acceleració del desgel del casquet de Groenlàndia podria tenir conseqüències sobre la futura estabilitat de la circulació oceànica i, per tant, sobre el desenvolupament del canvi climàtic.En la última glaciación, antes de que empezaran a deshacerse grandesmasas de hielo de los continentes y se vertieran en el Océano Ártico,unos primeros episodios esporádicos de deshielo en el antiguo manto dehielo que cubría las Islas Británicas ya afectaron la circulación de lascorrientes oceánicas, que juegan un papel clave en la estabilidadclimática del planeta. Este hecho sugiere que el calentamiento y laaceleración del deshielo del casquete de Groenlandia podría tenerconsecuencias para la futura estabilidad de la circulación oceánica y, portanto, para el desarrollo del cambio climático.At the end of the last ice age, before big ice masses dissolved on thecontinents surrounding the North Atlantic Ocean, some sporadicepisodes of rapid melting of the ancient British Ice Sheet affected oceancurrents that are very important for Earth's climatic stability. This factsuggests that the warming and accelerated melting of the Greenland IceSheet could have consequences for the stability of ocean circulation, andfor the future climatic development

La fi de l'última glaciació va incrementar ràpidament el CO2 de l'atmosfera

Una recerca publicada a Nature descriu per primer cop com el desgel de l'última glaciació i les modificacions en els corrents van alliberar a l'atmosfera grans quantitats de CO2 emmagatzemades al fons dels oceans, tot accelerant l'escalfament del planeta per efecte hivernacle i la fi de l'era glacial. La recerca, on ha participat l'investigador ICREA de la UAB, Rainer Zahn, ha desvetllat la combinació d'efectes que va provocar aquest alliberament en els dos hemisferis, a partir de l'estudi de les concentracions de components isotòpics en microfòssils marins. Aquest nou resultat posa en relleu un important mecanisme pel qual l'oceà influeix en les concentracions atmosfèriques de CO2.Una investigación publicada en Nature describe por primera vez cómo el deshielo de la última glaciación y las modificaciones en las corrientes liberaron a la atmósfera grandes cantidades de CO2 almacenadas en el fondo de los océanos, acelerando el calentamiento del planeta por efecto invernadero y el fin de la era glacial. La investigación, en la que ha participado el investigador ICREA de la UAB, Rainer Zahn, ha desvelado la combinación de efectos que provocó esta liberación en los dos hemisferios, a partir del estudio de las concentraciones de componentes isotópicos en microfósiles marinos. Este nuevo resultado pone de relieve un mecanismo importante por el cual el océano influye en las concentraciones atmosféricas de CO2.A research published in Nature for the first time describes how the thaw of the last glacial age produced changes in ocean currents which caused large quantities of CO2 stored deep in the oceans to be released into the atmosphere. This gave way to an acceleration in the rise of the planet's temperature due to the greenhouse effect and the end of the glacial period. The research was carried out with the participation of UAB's ICREA researcher Rainer Zahn, who described the combination of effects these emissions caused in the two hemispheres by studying concentrations of isotopic components in marine microfossils. The result of this study reveals an important mechanism and the influence of the ocean in CO2 concentrations found in the atmosphere

Un canvi climàtic fa 20.000 anys va invertir la circulació a l'Atlàntic

Investigadors de la UAB han publicat a Nature un estudi que mostra com van canviar els corrents oceànics a l'Atlàntic a causa del canvi climàtic en el passat. La recerca demostra que hi va haver un període en què es va invertir el règim de circulació de les aigües profundes. Els resultats són rellevants per al futur proper, ja que s'espera que es produeixin canvis similars en el marc de l'escalfament del clima al llarg dels propers cent anys.Investigadores de la UAB han publicado en Nature un estudio que muestra cómo cambiaron las corrientes marinas en el Atlántico a causa del cambio climático en el pasado. La investigación demuestra que hubo un periodo en que se invirtió el régimen de circulación de las aguas profundas. Los resultados son relevantes para el futuro próximo, ya que se espera que se produzcan cambios similares en el marco del calentamiento del clima a lo largo de los próximos cien años.UAB researchers have offered details in an article published in Nature on a study which shows how ocean currents in the Atlantic were affected by climate change in the past. The study shows that there was a period when the flow of deep waters in the Atlantic was reversed. The results are relevant for the near future since similar changes are expected to occur in the course of climate warming over the next 100 years

Exceptional Agulhas leakage prolonged interglacial warmth during MIS 11c in Europe

The transport of warm and saline surface water from the Indo-Pacific Ocean into the South Atlantic ("Agulhas leakage") influences the Atlantic Meridional Overturning Circulation (AMOC), which in turn exerts control on European climate. Paleoceanographic data document a remarkably strong Agulhas leakage at the end of marine isotope stage (MIS) 11c interglacial (~400 ka B.P.), which is one of the best orbital analogues for the Holocene. Here we assess the potential influence of this exceptional Agulhas leakage on North Atlantic climate based on a compilation of marine and terrestrial proxy records from the Iberian margin and continental Europe. We show that a ~5 ka long warm period persisted across Europe beyond the MIS 11c climatic optimum. This warm period is testified by increases in foraminifer-derived sea surface temperatures on the Iberian margin, a spread of temperate trees on Iberia, and the expansion both of evergreen trees and thermophilous diatom taxa in Central European lowlands. Paradoxically, this warming coincides with an insolation minimum, implying that orbital forcing can be excluded as the underlying cause. We conclude that persistent warmth during weak insolation at the end of MIS 11c in Europe may have been triggered by strengthened Agulhas leakage, which stimulated a vigorous AMOC and increased the northward transport of warm surface waters to higher latitudes via the North Atlantic Current. The close analogy of the present and MIS 11c orbital forcing underlines the possibility that the present-day increase of the Agulhas leakage, although driven by different forcing than MIS 11c, may considerably affect future climates across Europe

North Atlantic thermohaline circulation during the last glacial period : evidence for coupling between meltwater events and convective instability

Available from TIB Hannover: RR 1846(63) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Centennial-scale variability of the British ice sheet: implications for climate forcing and Atlantic meridional overturning circulation during the last deglaciation

Evidence from paleoclimatic archives suggests that Earth's climate experienced rapid temperature changes associated with pronounced interhemispheric asymmetry during the last glacial period. Explanations for these climate excursions have converged on nonlinear interactions between ice sheets and the ocean's thermohaline circulation, but the driving mechanism remains to be identified. Here we use multidecadal marine records of faunal, oxygen isotope, and sediment proxies from the northeast Atlantic proximal to the western margins of the last glacial British Ice Sheet (BIS) to document the coupling between ice sheet dynamics, ocean circulation, and insolation changes. The core data reveal successions of short-lived (80-100 years), high-amplitude ice-rafted debris (IRD) events that were initiated up to 2000 years before the deposition of detrital carbonate during Heinrich events (HE) 1 and 2. Progressive disintegration of the BIS 19-16 kyr before present (B.P.) occurred in response to abrupt ocean-climate warmings that impinged on the northeast Atlantic during the early deglaciation. Peak IRD deposition recurs at 180-220 year intervals plausibly involving repeated breakup of glacial tidewater margins and fringing marine ice shelves. The early deglaciation culminated in a major meltwater pulse at ∼16.3 kyr B.P. followed by another discharge associated with HE1 some 300 years after. We conclude that temperature changes related to external forcing and marine heat transport caused a rapid response of the BIS and possibly other margins of the Eurasian Ice Sheet. Massive but short-lived meltwater surges influenced the Atlantic meridional overturning circulation thereby contributing to North Atlantic climate variability and bipolar climatic asymmetr

Millennial-scale surface and subsurface paleothermometry from the northeast Atlantic, 55-8 ka BP

We present high-resolution records of upper ocean temperatures derived from Mg/Ca ratios of surface-dwelling Globigerina bulloides and subsurface-dwelling Neogloboquadrina pachyderma sinistral and the relative abundance of N. pachyderma sinistral for the period 55-8 ka BP from NE Atlantic sediment core MD01-2461. Millennial-scale temporal variability and longer-term trends in these records enable us to develop a detailed picture of past ocean conditions such as a weakening of thermocline intensity from marine isotope stage 3 (MIS 3) to the last glacial maximum (LGM). The correspondence of all temperature proxies and convergence of paired oxygen isotope (δ18O) records from both planktonic species implies a breakdown in the thermocline and year-round mixing of the upper water column through the LGM, perhaps related to decreasing insolation and additional cooling in association with the expansion of the circum-North Atlantic ice sheets. Millennial-scale divergence in surface and subsurface temperatures and δ18O across the last glacial correspond to meltwater release and the development of a strong halocline associated with both Heinrich (H) events and instabilities of the NW European ice sheet. During such episodes, G. bulloides Mg/Ca appears to record ambient, even warming summer sea surface temperatures across H events while the other proxies record maximum cooling