Impact of freshwater release in the Mediterranean Sea on the North Atlantic climate

Swingedouw, Didier; Colin, Christophe; Eynaud, Frédérique; Ayache, Mohamed; Zaragosi, Sébastien

doi:10.1007/s00382-019-04758-5

Cited by 11 publications

(13 citation statements)

References 74 publications

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“…Paleoceanography and Paleoclimatology of the Atlantic and consequently on Atlantic Meridional Overturning Circulation (AMOC) and heat transport to the high latitudes Ivanovic et al, 2014;Kida et al, 2008;Ozgokmen et al, 2001;Rahmstorf, 1998;Reid, 1979;Rogerson et al, 2006;Swingedouw et al, 2019). On the other hand, changes in the AMOC and the physical properties of the Atlantic intermediate and deep water masses could also affect the MOW settling depth in the Atlantic.…”

Section: 1029/2020pa003931mentioning

confidence: 99%

“…It spreads between 500 and 1,500 m and can eventually reach the high latitudes of the North Atlantic (Bashmachnikov et al, 2015; Bryden & Stommel, 1984; Iorga & Lozier, 1999; Mauritzen et al, 2001; Ozgokmen et al, 2001; van Aken, 2000a). Any change in the physicochemical properties of this water mass in response to Mediterranean pumping of heat and salt may have an important impact on the vertical density gradient of the Atlantic and consequently on Atlantic Meridional Overturning Circulation (AMOC) and heat transport to the high latitudes (Bethoux et al, 1999; Ivanovic et al, 2014; Kida et al, 2008; Ozgokmen et al, 2001; Rahmstorf, 1998; Reid, 1979; Rogerson et al, 2006; Swingedouw et al, 2019). On the other hand, changes in the AMOC and the physical properties of the Atlantic intermediate and deep water masses could also affect the MOW settling depth in the Atlantic.…”

Section: Introductionmentioning

confidence: 99%

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Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

Sierro

Hodell

Andersen

et al. 2020

Paleoceanog and Paleoclimatol

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To investigate past changes in the Mediterranean Overflow Water (MOW) to the Atlantic, we analyzed the strength of the MOW and benthic δ 13 C along the last 250 kyr at Integrated Ocean Drilling Program (IODP) Site U1389 in the Gulf of Cadiz, near the Strait of Gibraltar. Both the strength of the MOW and the benthic δ 13 C were mainly driven by precession-controlled fluctuations in the Mediterranean hydrologic budget. Reduced/enhanced Nile discharge and lower/higher Mediterranean annual rainfall at precession maxima/minima resulted in higher/lower MOW strengths at Gibraltar and stronger/weaker Mediterranean overturning circulation. At millennial scale, the higher heat and freshwater loss to the atmosphere during Greenland stadials increased buoyancy loss in the eastern Mediterranean. This enhanced the density gradient with Atlantic water, resulting in a higher MOW velocity in the Gulf of Cadiz. Unlike non-Heinrich stadials, a lower-amplitude increase in velocity was seen during Heinrich stadials (HSs), and a significant drop in velocity was recorded in the middle phase. This weak MOW was especially recognized in Termination I and II during HS1 and HS11. These lower velocities at the depth of Site U1389 were triggered by MOW deepening due to the lower densities of Atlantic intermediate water caused by freshwater released from the Laurentide and Eurasian ice sheets. The intrusion of salt and heat at deeper depths in the Atlantic during HSs and its shoaling at the end could have contributed to drive the changes in the Atlantic Meridional Overturning Circulation during Terminations.

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Section: 1029/2020pa003931mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

Sierro

Hodell

Andersen

et al. 2020

Paleoceanog and Paleoclimatol

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“…MOW provides a salt source for intermediate depths of the North Atlantic, but the effects of this input are not well understood. It is widely (but not universally) suggested that the salt supplied by MOW significantly increases the rate of North Atlantic overturning today and had variable impacts during the last glacial cycle (Bahr et al, 2018; Llave et al, 2006; Rogerson et al, 2010, 2012; Swingedouw et al, 2019; Voelker et al, 2006). MOW probably exerts significant circulatory impact following Greenland stadials, forming a crucial part of the negative feedback mechanism that promotes the reinstatement of vigorous North Atlantic deepwater formation and overturning from its weakened cold‐interval state (Llave et al, 2006; Voelker et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, significant reorganizations of shallow and intermediate water mass structure in the North Atlantic may arise in response to changes in MOW‐injection depth (Ivanovic, Valdes, Flecker, et al, 2013; Ivanovic, Valdes, Gregoire, et al, 2013) and the strength of the Azores Current, and consequently, European ice sheet dynamics are sensitive to MOW entrainment into North Atlantic intermediate water masses (Kaboth‐Bahr et al, 2018). In contrast to the idea that increased MOW‐fed salinity to the North Atlantic enhances overturning circulation, one recent numerical analysis of the impact of sapropel events suggests that the upper AMOC cell may weaken or strengthen, depending on the rate of freshwater input to the Mediterranean (Swingedouw et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Climate‐Induced Variability in Mediterranean Outflow to the North Atlantic Ocean During the Late Pleistocene

Nichols

Xuan

Crowhurst³

et al. 2020

Paleoceanog and Paleoclimatol

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Mediterranean Outflow Water (MOW) adds salt and density to open ocean intermediate waters and is therefore an important motor of Atlantic meridional overturning circulation (AMOC) and climate variability. However, the variability in strength and depth of MOW on geological timescales is poorly documented. Here we present new detailed records, with excellent age control, of MOW variability from 416 ka to present from rapidly accumulated marine sediments recovered from the West Iberian Margin during Integrated Ocean Drilling Program (IODP) Expedition 339. Our records of X-ray fluorescence (XRF), physical grain size, and paleocurrent information from the anisotropy of magnetic susceptibility (AMS) indicate (i) a close relationship between the orientation of principle AMS axes and glacial-interglacial cycles and (ii) two distinct regimes of MOW behavior over the last~416 kyr in grain-size and AMS variability at orbital (mainly precessional) and suborbital timescales. Between marine isotope stage (MIS) 10 and MIS 4, MOW was focused at a generally shallow depth on the West Iberian Margin, and changes in MOW strength were strongly paced by precession. A transition interval occurred during MISs 5 and 4, when MOW deepened and millennial-scale variability in flow strength was superimposed on orbitally paced change. During MIS 11 and from MIS 3 to present, MOW was deeply focused and millennial-scale variability dominated. We infer that late Pleistocene variability in MOW strength and depth were strongly climate influenced and that changes in circum-Mediterranean rainfall climate were likely a primary control. Plain Language Summary Mediterranean Outflow Water (MOW) is a salty, dense water body flowing from the Mediterranean into the North Atlantic. Today, MOW encourages North Atlantic overturning circulation and influences regional and global climate. However, changes in MOW strength and depth on geological timescales are poorly documented limiting our understanding of the relationships between climate, ocean circulation, and MOW. We analyzed magnetic properties, chemical composition, and grain size of sediment cores recovered off the Portuguese coast. We dated these archives by correlating variability in their chemical composition to a nearby site with well-established chronology. We find two modes of variability in MOW strength and depth. Between 370 and 130 ka, MOW was located above our study site during warm intervals and was present during cold intervals. Changes in MOW strength were paced by the influence of the precession (wobble) of Earth's rotation axis on incoming solar radiation. After 130 ka, variabilities in MOW strength and depth transitioned to a shorter timescale mode of operation, in step with abrupt climate events. The sign of change in MOW strength and the pattern of change in pacing indicate that the primary forcing factor was changes in rainfall climate in and around the Mediterranean.

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“…jussieu.fr/igcmg_doc/wiki/Doc/Models/LMDZ (last access: May 2020) and http://forge.ipsl.jussieu.fr/nemo/wiki/Users (last access: May 2020) under the terms of the CeCill license for both LMDZ and NEMO. The exact version of the model used to produce the results used in this paper is archived on Zenodo (Vadsaria et al, 2019), as are input data and scripts to run the model and produce the plots for all the simulations presented in this paper.…”

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confidence: 99%

Development of a sequential tool, LMDZ-NEMO-med-V1, to conduct global-to-regional past climate simulation for the Mediterranean basin: an Early Holocene case study

Vadsaria¹,

Li²,

Ramstein³

et al. 2020

Geosci. Model Dev.

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Abstract. Recently, major progress has been made in the simulation of the ocean dynamics of the Mediterranean using atmospheric and oceanic models with high spatial resolution. High resolution is essential to accurately capture the synoptic variability required to initiate intermediate- and deep-water formation, the engine of the Mediterranean thermohaline circulation (MTC). In paleoclimate studies, one major problem with the simulation of regional climate changes is that boundary conditions are not available from observations or data reconstruction to drive high-resolution regional models. One consistent way to advance paleoclimate modelling is to use a comprehensive global-to-regional approach. However, this approach needs long-term integration to reach equilibrium (hundreds of years), implying enormous computational resources. To tackle this issue, a sequential architecture of a global–regional modelling platform has been developed for the first time and is described in detail in this paper. First of all, the platform is validated for the historical period. It is then used to investigate the climate and in particular, the oceanic circulation, during the Early Holocene. This period was characterised by a large reorganisation of the MTC that strongly affected oxygen supply to the intermediate and deep waters, which ultimately led to an anoxic crisis (called sapropel). Beyond the case study shown here, this platform may be applied to a large number of paleoclimate contexts from the Quaternary to the Pliocene, as long as regional tectonics remain mostly unchanged. For example, the climate responses of the Mediterranean basin during the last interglacial period (LIG), the Last Glacial Maximum (LGM) and the Late Pliocene all present interesting scientific challenges which may be addressed using this numerical platform.

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Impact of freshwater release in the Mediterranean Sea on the North Atlantic climate

Cited by 11 publications

References 74 publications

Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

Climate‐Induced Variability in Mediterranean Outflow to the North Atlantic Ocean During the Late Pleistocene

Development of a sequential tool, LMDZ-NEMO-med-V1, to conduct global-to-regional past climate simulation for the Mediterranean basin: an Early Holocene case study

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