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MAGY project: MAllorca hydroloGY over the last few centuries. Instrumental validation of speleothem archives
(International Union for Quaternary Research, 2023-07) Torner Perez, Judit; Cacho Lascorz, Isabel; Català, Albert; Cisneros Bermejo, Mercè; Fornós, Joan J. (Joan Josep); Moreno, A.; Bladé, Ileana; Cheng, Hai; Edwards, R. Lawrence; Stoll, Heather
Geochemical analyses of speleothems and cave monitoring offer a complete framework for cave systems concerning hydrological changes and climate variability at very different timescales. In this regard, one critical target becomes the period when paleoclimatic records overlap with the directly measured instrumental records of climate. In order to improve the interpretation of speleothems as paleoclimatic records and therefore elucidate past climate changes in the western Mediterranean region, the MAGY project intent is the comparison of a new collection of speleothem records from Mallorca Island, which spans the last centuries, with precipitation and temperature data acquired in the weathering station from the Mallorca airport. This information is particularly critical on this island which is likely to face high hydrological stress under the current conditions of climate change. The implementation of this study requires high-resolution trace element profiles obtained by LA-ICP-MS to detect even seasonality variability in the speleothems and parallel well-resolved age models. The combination of U/Th dating, the 14C technique, and the confocal laser scanning microscopy technique, which allows annual layer counting, will provide solid chronologies. Preliminary results show that the Mg/Ca signal corresponds with the precipitation patterns recorded by regional instrumental records.
Mediterranean thermohaline circulation variability from the last deglaciation associated with changes in the eastern Mediterranean water outflow
(International Union for Quaternary Research, 2023-07) Trias Navarro, Sergio; Pena González, Leopoldo David; De la Fuente, María; Paredes, Eduardo; Garcia Solsona, Ester; Frigola Ferrer, Jaime I.; Català, Albert; Lirer, Fabrizio; Haghipour, N.; Pérez-Asensio, José N. (José Noel); Cacho Lascorz, Isabel
The Eastern Mediterranean Sourced Water (EMSW) outflow through the Strait of Sicily and together with the Western Mediterranean Deep Water (WMDW) contribute with different proportion to the Mediterranean outflow waters (MOWs) that exit into the Atlantic Ocean through the Strait of Sicily. In this work, we investigate changes in the EMSW outflow from the last deglaciation, with special focus in two periods characterized by important hydrographic changes, 1) The Younger Dryas (YD) and 2) the Last sapropel (S1). For that, we analyze Neodymium isotopes in planktic foraminifera coatings, stable oxygen isotopes and Mg/Ca ratios from both benthic and planktic foraminifera as well as grain-size from a sediment core recovered at the western flank of Sicily channel at 1066 m depth (W-Sicily; NDT-6-2016). At present, this site is located below the hydrographic boundary layer between the eastern and western sourced water-masses and then, it is suitable to evaluate changes in the EMSW outflow. Our data suggests that enhanced and high-salinity flow of eastern Mediterranean sourced waters (EMSWs) during the YD resulted on an intensification of Mediterranean outflowing waters (MOWs) currents. We proposed that this enhanced MOW could have favored the reactivation of the Atlantic meridional overturning circulation (AMOC), which was operating in a weak mode. An important reduction of the EMSW flow during the S1 resulted in a reduced surface Atlantic water eastward flow, reducing its influence at W-Sicily. During the last part of the S1 (S1b) very distinctive hydrographic conditions developed both at surface, with strong mixing, and at depth with the appearance of a high salinity water mass. We propose that regional climate conditions led to an increase of the evaporation/precipitation, which would have favored deep water convection processes, promoting the formation of a high-salinity intermediate-water mass over the Tyrrhenian Sea area during this S1b period.
The last deglaciation in the SW Iberian margin: changes in the Atlantic surface and Mediterranean bottom waters
(International Union for Quaternary Research, 2023-07) Tarruella, J. P.; Català, Albert; Cacho Lascorz, Isabel; Béjard, T. M.; Sierro, F.
The transition from the Last Glacial Maximum to the Holocene interglacial period is marked by abrupt global changes in which ocean thermohaline circulation, ice sheets and atmosphere interacted. Mediterranean overturning circulation and thus Mediterranean outflow were strongly influenced by these changes and might even have played a role by exporting heat and salt to the North Atlantic. The gulf of Cádiz Contourite Depositional System is characterized by the presence of two sandy contourite layers, corresponding to periods of reduced Atlantic Overturning Circulation (AMOC) during late Heinrich stadial 1 and Younger Dryas. In this work we present new multiproxy record for last 30ka from a sediment core located in the main branch of Mediterranean overflow. Planktic foraminifera assemblages have been used to reconstruct North Atlantic-influenced sea surface temperatures (SST), and Mg/Ca in benthic foraminifera to reconstruct Mediterranean overflow-influenced seawater bottom temperature (SBT). Results from planktic foraminifera are well correlated with what is recorded in nearby sites, marked by an abrupt SST drop during Heinrich event 1 and relatively high SST during LGM. Sea bottom temperatures raised gradually from Greenland stadial 3, as observed in Greenland ice temperature records, showing relatively warm values during LGM as noticed in SST. We suggest that this synchronism between Mediterranean deep water and Greenland air temperatures trends can be explained by the atmospheric teleconnection between both regions. Cool air temperatures in Greenland are transferred to the Mediterranean through winter winds that caused surface water cooling and sinking to the deep Mediterranean. This long-term warming trend that reflects the average temperature of Mediterranean deep water was punctuated by by two events of higher temperatures at times of Sandy Contourite layers deposition (Late Heinrich stadial and late Younger Dryas). These pulses of heat and salt export to the North Atlantic just before the onset of AMOC restoration are consistent with the hypothesized Mediterranean Outflow contribution during Terminations.
Environmental conditions controlling Cold-water corals occurrence in western Melilla (western Mediterranean) since the last deglaciation
(International Union for Quaternary Research, 2023-07) Selvaggi, M.; De la Fuente, María; Lo Iacono, Claudio; Haghipour, N.; Català, Albert; Pérez-Asensio, José N. (José Noel); Cacho Lascorz, Isabel
Cold-water corals (CWCs) are widely scattered in the southern Alboran Sea (westernmost Mediterranean), specifically in the so-called East and West Melilla CWC mound provinces (EMCP, WMCP). In this study, we present hydrographical changes in West Melilla from the sediment core MD13-3451 (370 m water depth) across the last ~14.2 kyr BP, followed by an integrated assessment of the WMCP complex evolution. The detected temporal mound occurrence allowed the identification of CWCs development’ patterns since the last deglaciation, and relate them to distinct palaeoceanographic changes that potentially influenced the local environment framework. The performed analyses include both sedimentary characteristics (i.e., grain-size records), and geochemical measurements in benthic foraminifera calcite, i.e., stable isotopes and trace elements, such Mg/Ca as a proxy for deep-water temperatures (DWTs). Furthermore, seawater δ18O (δ18Osw) and seawater δ18O corrected for the ice volume signal (δ18Ow-ivc) have been estimated via paired analyses of Mg/Ca and δ18Ocarbonate. The generated data suggest: i) CWCs develop well with relatively warm DWTs and high currents intensities, although these factors are here not considered to be determinant in their formation. This also account for the oxygen content, where major changes does not seem to affect CWCs development. ii) Major changes concerning the hydrographical conditions occurred during the Early Holocene, where a rapid freshening of the waters is detected. The presented results, when combined with available records from neighbor sites, permitted to observe that CWCs proliferation or decline is closely coupled to the reorganization of the whole Alboran Sea’ water column structure. For instance, the Holocene decrease of CWCs growth occur simultaneously when intermediate water properties above ~400 m water depth became very distinctive from those below, suggesting a higher influence of isotopically lighter water masses. This point to the important role of Mediterranean Circulation in driving the development of coral mounds. Overall, our data provide a high-resolution record of the most recent hydrographic changes in the southern Alboran Sea, and also reflect the importance of integrating a wide range of environmental variables to better understand the complex interplay that controls CWCs development.
Rapid response of the Adriatic convection cell during the Sapropel S1: New insights from Nd isotopes
(International Union for Quaternary Research, 2023-07) Pena González, Leopoldo David; Checa, Helena; Margaritelli, Giulia; Frigola Ferrer, Jaime I.; Català, Albert; Garcia Solsona, Ester; Paredes, Eduardo; Rettori, Roberto; Lirer, Fabrizio; Cacho Lascorz, Isabel
The Sapropel events are intrinsically linked to changes in the Mediterranean thermohaline circulation (MedTHC). These organic-rich sedimentary layers that typically appear in the E-Mediterranean, have been often attributed to the combination of enhanced biological production in the surface ocean and to a deficit in the renewal rate of deep waters leading to severe anoxic conditions that helped preserving organic matter in the sediment. There is a general lack of knowledge on how the main intermediate and deep convection cells in the E-Med responded during sapropels. In this work we present a new reconstruction of the changes of the MedTHC circulation system during Sapropel 1 using Nd isotopes (εNd) in the Adriatic-North Ionian Sea region. The study site is located at the convergence and mixing between the outflow of Adriatic Deep Waters (ADW) and the arrival of E-Med Levantine Intermediate Water (LIW). New results using Nd isotope ratios illustrate changes in the mixing proportions of these two endmembers (ADW vs. LIW), and clearly show two distinctive collapse intervals during the sapropel (S1a and S1b) as a result of reduced strength in the ADW convection cell and increased presence of LIW. The two sapropel intervals where rapidly interrupted but a relatively short period where ADW resumed its convection and outflow into the north Ionian Sea. Further support to this interpretation comes from U/Mn ratios measured in foraminifera, gran size measurements as well as benthic foraminiferal fauna supporting the idea that the changes in the intensity of deep water convection preceded both the establishment of anoxic conditions at depth and the increased organic matter export to the sediments. By using an stochastic box model of the Mediterranean Sea enabled for isotopic tracers in seawater following a Monte-Carlo approach we demonstrate that the Nd isotpe resutls measured in the north Ionian Sea are consistent with a complete shutdown of the ADW outflow during the sapropel events. The collapse of ADW convection cell led the deposition of the last sapropel layer and favoured the dominance of LIW at intermediate depths in the E-Med water column.
Last deglacial reorganization of the western Mediterranean thermohaline circulation: evidences from sedimentological and Nd isotopes proxies
(International Union for Quaternary Research, 2023-07) Frigola Ferrer, Jaime I.; Pena González, Leopoldo David; Campderrós Serra, Sara; Català, Albert; De la Fuente, María; Garcia Solsona, Ester; Martin, C.; Merchán, A.; Paredes, Eduardo; Selvaggi, M.; Torner Perez, Judit; Trias Navarro, Sergio; Margaritelli, Giulia; Pérez-Asensio, José N. (José Noel); Lirer, Fabrizio; Cacho Lascorz, Isabel
Last glacial/interglacial transition involved significant changes in western Mediterranean (Med) thermohaline circulation that culminated with the formation of an organic rich layer (ORL) in the Alboran Sea from 14.5 to 9 ka BP. This event pre-dated the eastern Med stagnation associated with the Last Sapropel (S1: 10.8-7.1 kyr BP). Here we aim to gain in the understanding that those two events had in the oceanography of the westernmost Med and ultimately its impact on the Med outflow waters (MOW). Our approach combines sedimentological indicators (grain-size and XRF-core scanner data) with Nd isotopes measured in foraminifera diagenetic coatings as a proxy of water mass source. The studied material includes a set of cores covering a depth range from the Alboran Sea (from 300 to 1800 m) combined with a core from the Balearic Basin and another from the Gulf of Cadiz...
Deglacial Mediterranean-basins link: old carbon-enriched eastern waters and collateral consequences for western aragonite mounds growth
(International Union for Quaternary Research, 2023-07) De la Fuente, María; Selvaggi, M.; Skinner, L.; Lo Iacono, Claudio; Corbera Pascual, Guillem; Sadekov, A.; Scott, P.; Zhang, P.; Cheng, Hai; Rafter, P.; Haghipour, N.; Pena González, Leopoldo David; Català, Albert; Cacho Lascorz, Isabel
A Mediterranean Thermohaline Circulation slowdown related to deglaciation and monsoon dynamics have largely been discussed, but it yet remains insufficiently constrained. With the aim of investigating changes in water mass residence time (as a key parameter to elucidate inter-basin communication variations) and its potential environmental impacts, we present a multi-proxy-archive study in the Western Mediterranean mid-depth based on cold water corals radiocarbon ventilation ages, along with foraminiferal O2 and [CO32-] qualitative inferences. At ~300m, we find: 1) two aged-water pulses at Younger Dryas and ~8.2 event, respired carbon enriched and coincident with low CWC mound growth, and 2) a well-ventilated water pulse in between, parallel to a CWC mound flourishing stage. Our results allow changes in ventilation rates to be shown, quantified, and timed in association with periodical phases of MedTHC weakening, as well as suggesting enriched respired carbon episodes as a potential cause of decreased mound growth rates via aragonite dissolution.
Unveiling the variation in intermediate water mass circulation and its potential effects on Tunisian cold-water coral mound development during the last glacial cycle
(International Union for Quaternary Research, 2023-07) Corbera Pascual, Guillem; Lo Iacono, Claudio; Tejero, A.; De la Fuente, María; Garcia Solsona, Ester; Paredes, Eduardo; Pena González, Leopoldo David; Cacho Lascorz, Isabel
To date, most thriving cold-water coral assemblages in the Mediterranean Sea are found within the water depths bathed by the Levantine Intermediate Water (LIW). In a similar way, coral mound development in this basin has been partly linked to the distance between the mounds’ summit and the water mass interface found at the transition from Atlantic Water (AW) to LIW (ca. 200-250 m water depth). Water mass interfaces are characterised by sharp density gradients that promote the accumulation of particulate matter, mainly consisting of plankton. Additionally, the interaction between two water masses might promote the creation of internal waves that propagate along the interface, increasing sediment resuspension and vertical mixing, which could ultimately promote enhanced transfer of organic matter to the depths were the corals are found. Nonetheless, due to glacio-eustatic changes and other paleoclimatic variations, the depth and intensity of the AW-LIW interface are likely to change through time. In this regard, the present study aims to use gravity cores collected from on- and off-mound areas of the Tunisian Coral Mound Province to assess the potential variations in intermediate water mass circulation during the last glacial cycle and its effects on coral mound development. Specifically, we aim to use Nd isotopic analyses from both corals and foraminifera to describe the changes of water-mass influence in the area. These analyses will be complemented with grainsize and U/Mn data, extracted from foraminifera, in order to acquire a better understanding of the changes in intensity and oxygenation of the water mass bathing the mounds. The analyses of the samples is currently underway and thus, the preliminary data together with a corresponding discussion will be presented.
The Holocene expression in humidity and sea surface temperatures in the western Mediterranean Sea
(International Union for Quaternary Research, 2023-07) Català, Albert; Pena González, Leopoldo David; Garcia Solsona, Ester; Paredes, Eduardo; Frigola Ferrer, Jaime I.; Sanchez-Vidal, Anna; Calafat Frau, Antoni; Cacho Lascorz, Isabel
The Mediterranean region is particularly sensitive to global climate variability that critically reflects on its hydrological conditions. A recently published high-resolution reconstruction of Holocene Sea Surface Temperature (SST) based on Globigerina bulloides Mg/Ca ratios set the basis to explore, within a warm climatic period, the impact of North Atlantic oceanographic conditions shaping the properties of the inflowing waters into the Mediterranean Sea. Going a step further in establishing the potential links between these oceanographical changes with the hydrological conditions on the southern Iberian Peninsula, we isotopically characterized (Sr, Nd and Pb) the present terrigenous sourcing and their transport processes on the Alboran Sea to use as an analogue to reconstruct the Holocene variations. The present-day isotopic characterization was performed of settling particles recovered by moored sediment traps under well-characterized meteorological conditions. This reveals that the main sources of the terrigenous particles arrive transported by the fluvial discharges around the Alboran Sea. Also, the observed isotopic changes during the recorded year were closely linked to rainfall patterns. Transferring this knowledge to the past time and compared with the SST, the results indicate that the most humid and warmer conditions were developed during the Early Holocene. Afterwards, a transition towards colder temperatures was linked with an aridification and enhancement of the torrential rainfalls, culminating with the coldest SST and higher torrential effect. During the Late Holocene, relative cold and drier conditions similar to the present were recorded.
Present and past variability of the Mediterranean Outflow Water using Nd isotopes
(International Union for Quaternary Research, 2023-07) Campderrós Serra, Sara; Pena González, Leopoldo David; Cacho Lascorz, Isabel; Garcia Solsona, Ester; Paredes, Eduardo
The Mediterranean Outflow Water (MOW) is a source of heat and salt into the Atlantic Ocean, and it has been proposed that it preconditions the water masses that participate in the production of deep water into the north Atlantic, or the Atlantic Meridional Overturning Circulation (AMOC). Although some modelling and proxy studies have suggested that past changes in properties of the MOW could have consequences to the AMOC, this impact is still being debated. Seawater Nd isotopic composition (ƐNd) has been used as a conservative water mass tracer in the modern ocean, but also as a paleo-circulation proxy measured in the Fe-Mn coatings of foraminifera. One of the advantages of using Nd isotopes is that this tracer can be used to calculate the mixing and export rates of water masses nowadays, but also in the sedimentary record, which could help estimate the mixing and exportation rates of the MOW into the North Atlantic in the present and in the past. But recently, some studies have shown processes that can modify the signal of ƐNd in seawater and consequently, in the sedimentary archive (for example pore water reactions). In order to test the reliability of ƐNd as a tracer for the MOW, we analyze ƐNd from seawater samples, foraminifera Fe-Mn coatings and sediments from transects located in the Iberian Margin. Seawater results show that ƐNd can be used to identify the different water masses located in the Iberian Margin. Considering that the ƐNd values of the MOW differ from the values of the surrounding Atlantic waters, Nd isotopes seem to be a good tool to trace the MOW through the Iberian Margin. The comparison of these results with the ƐNd values of core-top foraminifera and sediment samples provides us with enough information to infer how the geochemical signal of seawater Nd isotopes is transferred to the Fe-Mn coatings of foraminifera, and how to interpret these results on a palaeoceanographic context. This study aims to establish the basses to interpret ƐNd reconstructions of MOW changes since the last glacial period in relation with AMOC changes.
Deglacial and Holocene changes in Mediterranean Thermohaline Circulation: A joint perspective from Eastern and Western basins [INQUA 2023]
(2023-07) Cacho Lascorz, Isabel; Català, Albert; Pena González, Leopoldo David; Frigola Ferrer, Jaime I.; Campderrós Serra, Sara; Inglavaga, R.; Martín Closas, Carles; Trias Navarro, Sergio; Checa, Helena; De la Fuente, María; Margaritelli, Giulia; Pérez-Asensio, José N. (José Noel); Lirer, Fabrizio
The dominant arid climate conditions over the Mediterranean (Med) control water properties and the formation processes of intermediate and deep water masses. Deep convection cells occur in both the E- and W-Med basins and there are interconnected through the intermediate waters mostly formed in the easternmost area of the Med. During last deglaciation and Holocene periods both E- and W-Med had experienced periods of major disruptions in deep convection. The last organic layer (ORL1) formed in the WMed during the deglacial period and later the last sapropel (S1) in the E-Med. Both enhanced productivity and enhanced stratification are regarded as the causes for the two events but responding to different drivers, the deglacial freshening in the case of the ORL1 and the African monsoon flooding for the S1.
Water export changes through the Strait of Sicily during the last deglacial period
(2023-09) Trias Navarro, Sergio; Pena González, Leopoldo David; De la Fuente, María; Paredes, Eduardo; Garcia Solsona, Ester; Frigola Ferrer, Jaime I.; Català, Albert; Caruso, Antonio; Lirer, Fabrizio; Haghipour, N.; Pérez-Asensio, José N. (José Noel); Cacho Lascorz, Isabel
The Mediterranean Sea is constituted by two sub-basins connected through the Sicily channel. In the western basin deep water is formed at Gulf of Lions and in the eastern basin deep water convection occurs in both the Adriatic and Aegean Sea, while intermediate water is formed in the Levantine Sea area. The intermediate and deep water convection of the Eastern Mediterranean has been proved to be highly sensitive to varying fresh water fluxes, associated with increased rainfall during the African Humid period (15-6 kyr BP). Here we investigate for the first time, changes in the export rates of eastern Mediterranean sourced water masses (EMSW) into the western basin for the last ~15 kyr BP. For this purpose, we analyze 143Nd/144Nd isotope ratios (eNd) in planktic foraminifera coatings, a quantitative tracer of water mass provenance, from a sediment core recovered at the western flank of the Sicily channel (NDT-6-2016, 1066 m depth). At present, this site is located below the hydrographic boundary layer between the eastern and western sourced water-masses. The measured eNd values were then used to elucidate changes in EMSW export rates through late deglacial and Holocene periods applying an endmember mixing model. Our results indicate that EMSW export rates were maximum during the Younger Dryas (YD) period, about three times higher than during the S1, supporting the limited formation of both intermediate and deep water masses in the eastern basin during the S1 as suggested by previous studies. We propose that the enhanced EMSW outflow into the western Mediterranean over the YD was the result of the combined effect of 1) enhanced climate-driven convection in the Aegean Sea and 2) the reduced convection of western deep water during this period, when the last Organic Rich Layer deposited in the deepest areas of the western basin.
New Mediterranean speleothem records for glacial Terminations IV and III
(2023-09) Torner Perez, Judit; Cacho Lascorz, Isabel; Stoll, Heather; Moreno Caballud, Ana; Cheng, Hai; Edwards, R. Lawrence
Speleothem archives spanning the glacial terminations IV and III (TIV and TIII) are particularly scarce in the western Mediterranean region. This study presents unprecedented geochemical records measured on a speleothem from Minorca Island that grew continuously through the period from Marine Isotope Stage 11 to 7. Its U/Th chronological model provides an accurate and excellent chronology for both terminations which are recognized as intervals with slow growth rates. Hence revealing the difficulty of the speleothem to grow during these periods of rapid melting, suggesting major distortions in the hydrological conditions associated to glacial terminations. The Mg/Ca and d13C records indicate that deglaciations were characterized by rapid transitions towards more humid conditions. However, the d18O results shows a deglacial freshening that led in time the hydrological signal, with a remarkably larger time-led at the TIV. These earlier depletions of the d18O are interpreted to mark the onset of the glacial melting, a freshening signal that propagated through the surface ocean and transferred from the rain source into the stalagmite. The co-existence of comparable deglacial d18O depleted episodes within the marine records, brings the possibility to review the marine chronologies, independently of the orbital tuning. An exercise that indicates a significant bias in the timing of the melting onset associated to TIV.
Collapse of the Mediterranean Thermohaline Circulation during the Sapropel S1: New insights from Nd isotopes
(2023-09) Pena González, Leopoldo David; Checa, Helena; Margaritelli, Giulia; Pérez-Asensio, José N. (José Noel); Català, Albert; Garcia Solsona, Ester; Paredes, Eduardo; Rettori, Roberto; Lirer, Fabrizio
Sapropel events, organic-rich sedimentary layers that typically appear in the E-Mediterranean, have been often attributed to a combination of enhanced biological production in the surface ocean as well as a deficit in the renewal rate of deep basin waters leading to severe anoxic conditions that helped with the preservation of organic matter in the sediment. The sapropels are intrinsically linked to changes in the Mediterranean thermohaline circulation (MedTHC), but little is known on the drivers of these changes. For example, there are no evidences on how the main intermediate and deep convection cells in the E-Med responded during sapropels. Here we present a new reconstruction of the changes of the MedTHC circulation system during Sapropel 1 using Nd isotopes (εNd) in the Adriatic-North Ionian Sea region. Our study core site is located at the mixing line between the formation of Adriatic Deep Waters (ADW) and the arrival of E-Med Levantine Intermediate Water (LIW). Our newly measured Nd isotope ratios thus reflect changes in the mixing proportions of these two endmembers (ADW vs. LIW), and clearly show two distinctive collapse phases during the sapropel (S1a and S1b) as a result of reduced strength in the ADW convection cell and increased presence of LIW. The two sapropel phases where interrupted but a relatively short period where ADW resumed its convection into the north Ionian Sea. Further support to this interpretation comes from U/Mn ratios measured in foraminifera as well as benthic foraminiferal fauna supporting the idea that the changes in the intensity of deep water convection preceded both the establishment of anoxic conditions at depth and the increased organic matter export to the sediments. We conclude that the collapse of ADW convection cell led the deposition of the last sapropel layer and favoured the dominance of LIW at intermediate depths in the E-Med water column.
A sedimentological insight into the deglacial reorganization of the Mediterranean thermohaline circulation
(2023-09) Frigola Ferrer, Jaime I.; Martín, C.; Merchán, A.; Pena González, Leopoldo David; Checa, Helena; Margaritelli, Giulia; Pérez-Asensio, José N. (José Noel); Català, Albert; Lirer, Fabrizio; Cacho Lascorz, Isabel
During the last deglaciation and early Holocene significant oceanographic changes have been observed in both western and eastern Mediterranean basins. Post glacial sea level rise strongly reduced the northwestern overturning cell from 14.5 to 9 ka BP, which favored the formation of an organic rich layer in the Alboran Sea. Increased river runoff in the east-Med enhanced water column stratification leading to the formation of Sapropel 1 between 10.8-6.1 ka BP. Although asynchronous and triggered by independent mechanisms, these basin-scale oceanographic changes had a profound impact on the water exchange between both basins and the Mediterranean thermohaline circulation, and consequently, in the amount and properties of Mediterranean waters exported to the north Atlantic region. Our grain-size and geochemical records show coetaneous decrease/increase from cores at deep/ intermediate levels of the west-Med confirming a major reduction of deep water currents in the deepest part of the basin related to the post glacial sea level rise, while increased intensity of currents at intermediate levels. These results likely suggest a significant change in the water masses properties during the deglaciation that would favored formation of intermediate water. On the other hand, the sedimentological records from an Ionian Sea sediment core show enhanced deep water currents during the first phase of the deglaciation, and a very marked reduction in the 10.8-7.5 ka time-interval, coinciding with the Sapropel 1 formation. Our results show that intermediate levels circulation was reinforced in both eastern and western Mediterranean basins during the first phase of the deglaciation likely suggesting a major export of intermediate water masses from the eastern to the western basin. Finally, the strong stratification leading formation of the Sapropel 1 produced a major reduction of deep water ventilation in the eastern basin that could also affect westward export of intermediate waters.
Holocene humidity changes in southern Iberia inferred from the geochemical signature of marine sediments
(2023-09) Català, Albert; Pena González, Leopoldo David; Garcia Solsona, Ester; Paredes, Eduardo; Frigola Ferrer, Jaime I.; Sanchez-Vidal, Anna; Calafat Frau, Antoni; Cacho Lascorz, Isabel
The Mediterranean region is particularly sensitive to global climate variability that critically reflects on its hydrological conditions. A recently published high resolution reconstruction of Holocene Sea Surface Temperature (SST) based on Globigerina bulloides Mg/Ca ratios, set the basis to explore, within a warm climatic period, the impact of North Atlantic oceanographic conditions shaping the properties of the inflowing waters into the Mediterranean Sea. Here we go a step further in establishing the potential links between these oceanographical changes with the hydrological conditions on the southern Iberian Peninsula.
Deglacial and Holocene changes in Mediterranean Thermohaline Circulation: A joint perspective from Eastern and Western basins
(2023-09) Cacho Lascorz, Isabel; Català, Albert; Pena González, Leopoldo David; Frigola Ferrer, Jaime I.; Campderrós Serra, Sara; Inglavaga, R.; Martín Closas, Carles; Trias Navarro, Sergio; Checa, Helena; De la Fuente, María; Margaritelli, Giulia; Pérez-Asensio, José N. (José Noel); Lirer, Fabrizio
The dominant arid climate conditions over the Mediterranean (Med) control water properties and the formation processes of intermediate and deep water masses. Deep convection cells occur in both the E- and W-Med basins and there are interconnected through the intermediate waters mostly formed in the easternmost area of the Med. Model projections anticipate that the current situation of climate change will led to an overall weakening of this circulation system during the current century. But the natural range of variability in the intensity of individual cells, the drivers and the inter-connection patterns between the cells is not well stablished. During the recent past (las deglaciation and current Holocene) both E- and W-Med had experienced periods of major disruptions in convection. The last organic layer (ORL1) formed in the W-Med during the deglacial period and later the last sapropel (S1) in the E-Med. Both enhanced productivity and weakening in convection are regarded as the causes in the two events but due to different drivers, the deglacial freshening in the case of the ORL1 and the African monsoon flooding for the S1. Here we present U/Mn ratios measured in the foraminifera diagenetic coatings from sediment cores from both E- and W-Med. The nature of this proxy, that provides information of the oxygen water content, allows its application in a wide range of oceanographical/oxygen conditions, a situation that limits other proxies whose carrier is very sensitive to oxygen content. This approach allows us, by the first time, to compare the oxygen evolution of individual basins and at different water depths by means of the same tool. The comparison with other available proxies let us to interpret the drivers of the changes and analyze the evolution of Med deep and intermediate convection along the ORL1 and S1. This new view advocates for a very close link between these two events but with very distinctive response of the individual cells to the dominant forcings.
Deglacial-Holocene Pulses of Old Carbon-Enriched Mediterranean Water Masses: Implications for Aragonite Mounds Growth and Global Carbon Cycle
(2023-09) De la Fuente, María; Selvaggi, M.; Lo Iacono, Claudio; Skinner, L.; Sadekov, A.; Scott, P.; Zhang, P.; Cheng, Hai; Rafter, P.; Haghipour, N.; Paredes, Eduardo; Pena González, Leopoldo David; Català, Albert; Cacho Lascorz, Isabel
Major changes in the Mediterranean Thermohaline Circulation (MedTHC) related to deglaciation and monsoon dynamics have been documented, while in turn, Mediterranean waters have been proposed to play a role back in global climate variability, ocean circulation and carbon cycle budgets, for instance via changes in water mass residence times. The 14C offset between coeval planktonic and benthic foraminifera over time is a very useful tool to infer variations in the water column ventilation (with no biological interference) that becomes more accurate when combined with local paired 14C-U/Th analyses in cold-water corals (CWC). Here, we present a multi-proxy-archive study (i.e., estimates of reservoir ages, εNd, [CO3 2-], O2 and current speed) carried out on the on-mound sediment core MD13-3452 (305 m, West Melilla, Alboran Sea, Western Mediterranean), which investigates potential deglacial changes and triggers in deep reservoir ages, as well as possible impacts on CWC aragonite mound growth and on global carbon cycle.

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