A new perspective of the Alboran Upwelling System reconstruction during the Marine Isotope Stage 11: A high-resolution coccolithophore record

doi:10.1016/j.quascirev.2020.106520

Quaternary Science Reviews

Volume 245, 1 October 2020, 106520

https://doi.org/10.1016/j.quascirev.2020.106520 Get rights and content

Highlights

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A high-resolution coccolithophore primary productivity record in the Alboran Sea reveals climate fluctuations across MIS 11.
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Combination of nannofossil with terrestrial proxies evidence the control of two-phase atmospherical NAO-like.
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A high-frequency variability in the NAO-like phases is identified during the MIS12/MIS 11 and MIS 11 substages.
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A comparable pattern of Heinrich-type events 3 and 2 with He of the last glacial cycle in the Alboran Sea is evidenced.

Abstract

A high-resolution study of the MIS 12/MIS 11 transition and the MIS 11 (430–376 kyr) coccolithophore assemblages at Ocean Drilling Program Site 977 was conducted to reconstruct the palaeoceanographic and climatic changes in the Alboran Sea from the variability in surface water conditions. The nannofossil record was integrated with the planktonic oxygen and carbon stable isotopes, as well as the U^k'₃₇ Sea Surface Temperature (SST) at the studied site during the investigated interval. The coccolithophore primary productivity, reconstructed from the PPP (primary productivity proxy = absolute values of Gephyrocapsa caribbeanica + small Gephyrocapsa group) revealed pronounced fluctuations, that were strongly associated with variations in the intensity of the regional Alboran Upwelling System. The comparison of the nannoplankton record with opal phytolith content for the studied site and the already available pollen record at the nearby Integrated Ocean Drilling Program Site U1385, suggests an association of the upwelling dynamics with the variability of the North Atlantic Oscillation-like (NAO-like) phase. High PPP during positive (+) NAO-like phases is the result of intensified upwelling, owing to the complete development of the surface hydrological structures at the Alboran Sea. This scenario was identified during the MIS 12/MIS 11 transition (428-422 kyr), the late MIS 11c (405-397 kyr), and MIS11 b to MIS 11a (397-376 kyr). Two short-term minima in the PPP and SST were observed during MIS 11 b and were coeval with the North Atlantic Heinrich-type (Ht) events Ht3 (∼390 kyr) and Ht2 (∼384 kyr). Increased abundance of the subpolar Coccolithus pelagicus subsp. pelagicus and Gephyrocapsa muellerae was consistent with the inflow of cold surface waters into the Mediterranean Sea during the Ht events. Lowered PPP during negative (−) NAO-like phases is the result of moderate upwelling by the incomplete development of surface hydrological structures at the Alboran Sea. This scenario is expressed during the early MIS 11c (422-405 kyr). Overall, the results of our study provide evidence of the important role of atmospheric circulation patterns in the North Atlantic region for controlling phytoplankton primary production and oceanographic circulation dynamics in the Western Mediterranean during MIS 11.

Introduction

The Mid-Brunhes interval, spanning from Pleistocene Marine Isotope Stages (MIS) 14 to 9 (Barker et al., 2006; Jansen et al., 1986), is a critical period for global climate change. Following the Mid-Pleistocene transition, this interval contains the shift in ice age cycles, that lengthened from ∼ 40 to ∼100 kyr, leading to warmer interglacial phases (Berger and Wefer, 2003; Jansen et al., 1986; Lisiecki and Raymo, 2005) and glacial terminations of greater amplitude (Terminations I–V; Past Interglacials Working Group of PAGES, 2016) than before. Among the other interglacial periods of the Mid-Brunhes, MIS 11 (424-374 kyr; Lisiecki and Raymo, 2005) has been proposed as a model to analyse the natural climate variability for several reasons: (i) the intensity and duration of the warming (Bauch et al., 2012; Hodell et al., 2000; PAGES, 2016); (ii) the enhanced penetration of the warm waters poleward (Berger and Wefer, 2003); and (iii) the increase in atmospheric greenhouse gas concentrations (Raynaud et al., 2005; Yin and Berger, 2012). All these processes are considered as main drivers of the collapse of the Greenland and west Antarctica ice sheets, and resulted in the eustatic sea-level rising about 20 m higher than it currently is (Olson and Hearty, 2009; Raymo and Mitrovica, 2012; Reyes et al., 2014; Roberts et al., 2012). Termination V, at the MIS 12/MIS 11 transition (424 kyr; Lisiecki and Raymo, 2005), is furthermore regarded as the largest amplitude glacial/interglacial transition of the last 800 kyr (PAGES, 2016).

MIS 11 is often considered a potential analogue for the Holocene as there are multiple similarities between both intervals, including: (i) the similar orbital forcing parameters of low eccentricity, high obliquity, low precessional amplitude, and insolation geometry (Berger and Loutre, 1991; Loutre and Berger, 2003); (ii) the elevated atmospheric CO₂ levels (Droxler and Farrell, 2000); and (iii) a small amount of continental ice (Loutre and Berger, 2003) similar to present conditions (Candy et al., 2014; Rohling et al., 2010; Yin and Berger, 2012).

Several paleoclimate records evidence the prevalence of long-lasting (∼30 kyr) warm and stable conditions during the early substage of the full interglacial, MIS 11c period (Desprat et al., 2007; Martrat et al., 2007; McManus et al., 2003; Oppo et al., 1998; Stein et al., 2009; Voelker et al., 2010). Nevertheless, mid-latitude terrestrial climate-records indicate contrasting early climate instabilities during MIS 11c on centennial (Koutsodendris et al., 2010; Prokopenko et al., 2010; Tye et al., 2016) to millennial time-scales (Oliveira et al., 2016; Tzedakis et al., 2009), keeping the discussion open regarding the homogeneity of the latitudinal extent of the full interglacial conditions. Suborbital-scale climate instabilities are comparatively well recorded during MIS 11 b and MIS 11a (∼395-374 kyr), in the North Atlantic to the Iberian latitudes (de Abreu et al., 2005; Hodell et al., 2013; Martrat et al., 2007; Palumbo et al., 2013; Rodrigues et al., 2011; Stein et al., 2009; Voelker et al., 2010) and the western Mediterranean (Marino et al., 2018). The origin of these instabilities has been associated with the southward incursion of waters with an Arctic origin (e.g. Oppo et al., 1998), and their effect on weakening the North Atlantic Meridional Overturning Circulation and coupled atmospheric interactions (Barker et al., 2015; McManus et al., 2003).

The Alboran Sea is the westernmost basin of the Mediterranean Sea, and hence, it has a crucial role in forming climate connections with the North Atlantic (Cacho et al., 1999, 2000; Martrat et al., 2004; Sierro et al., 2005). The Alboran Sea thus represents a strategic location for the reconstruction of palaeoceanographic and paleoclimatic variability for the whole Mediterranean Basin (e.g., Ausín et al., 2015a,b; Bazzicalupo et al., 2018; Colmenero-Hidalgo et al., 2004). Currently, the variability in sea-level, temperature, and precipitation in the region is partially controlled by fluctuations in the atmospheric gradient between the Azores High-pressure (AH) and the Icelandic Low-pressure (IL) cells, which constitutes the North Atlantic Oscillation mode (NAO) of winter climate variability in the North Atlantic region (Hurrell, 1995; Lionello, 2012). The changing NAO-like phase has been identified as a triggering mechanism for paleoenvironmental oscillations in the western Mediterranean during the Holocene (Fletcher et al., 2013; Frigola et al., 2007), with effects on primary productivity in the Alboran Sea (e.g., Ausin et al., 2015b; Bazzicalupo et al., 2020).

The sensitivity of coccolithophores to the changing surface ocean physicochemical conditions (temperature, salinity, nutrient-concentrations, and turbulence) makes them a valuable tool for the reconstruction of rapid palaeoceanographic fluctuations (Baumann et al., 2005). The high accumulation rate and adequate preservations of nannofossil (calcite plates termed coccoliths) in sediments throughout the Atlantic and Mediterranean Iberian margins have allowed for a number of studies, revealing the strong dependence of the coccolithophore primary productivity and assemblage-structure on the global climate at orbital and suborbital/millennial-scale (Amore et al., 2012; Ausín et al., 2015a,b; Bazzicalupo et al., 2018; Colmenero-Hidalgo et al., 2004; Marino et al., 2018; Palumbo et al., 2013).

The main objective of the present study was the high-resolution reconstruction of environmental and climatic changes in the Alboran Sea during the MIS 12/MIS 11 transition and MIS 11. Considering the coccolithophore primary productivity patterns as a proxy to monitor the changes in the surface and subsurface water column conditions, we attempted to unravel the past variations in the oceanographic circulation and its atmospheric configuration forcing at the western Mediterranean region. We integrated the high-resolution coccolithophore primary productivity record –inferred from the nannofossil characterization and quantification–, with the high-resolution records of the stable δ¹⁸ O and δ¹³ C isotopes from the planktonic foraminifera Globigerina bulloides and the alkenone U^k'₃₇ Sea Surface Temperatures (SST) at Ocean Drilling Program (ODP) Site 977. Additionally, the record of the opal phytolith content at ODP Site 977 together with the Mediterranean forest pollen taxa at the Portuguese Iberian margin Integrated Ocean Drilling Program (IODP) Site U1385 from Oliveira et al. (2016), were used to reconstruct the response of the Alboran Sea to atmospheric precipitation and wind track configuration during the MIS 12/MIS 11 transition and MIS 11 and their connections with the paleoclimate and palaeoceanographic processes of the North Atlantic.

Section snippets

Oceanographic and atmospheric setting

ODP Site 977 is located in the Alboran Sea, a transitional area between the semi-enclosed Mediterranean Sea and the adjacent Atlantic Ocean. As such, the circulation in this region is intense and characterized by an anti-estuarine model, with surface inflow of relatively low saline waters from the Atlantic (Atlantic Water, AW), and the outflow in depth of highly saline Mediterranean waters (Mediterranean Outflow Water, MOW) through the narrow and shallow Strait of Gibraltar (Pistek et al., 1985

Site location and core materials

ODP Site 977 is located in the eastern basin of the Alboran Sea (36° 1.9ʹN, 1° 57.3ʹW; Figs. 1), 1984 m below sea level. The sediment composition of the studied interval corresponds to 67.49–58.64 corrected meters below sea floor (cmbsf) from cores 8 and 7 of hole 977 A. The correction was made to adjust the 10.01 and 10.03 m of recovery, respectively in core 8 and 7, to the standard core length of 9.5 m.

The core materials are composed by an open marine-hemipelagic facies of nannofossil-rich to

Chronological framework

The chronology of the sediments was established by correlating the SSTs of both ODP Site 977 and the North Atlantic mid latitude IODP Site U1313 (Stein et al., 2009), for which the available age model is based on the correlation of the benthic δ¹⁸O with the global LR04 stack (Voelker et al., 2010). As the SST at Sites 977 and 1313 is controlled by the Azores Current, we assumed that there would be synchronous variations. The adjustments for the studied interval were made by including five

Atmospheric control mechanisms on the Alboran Upwelling System

The recorded PPP values, ranging from 7 × 10⁹ to 41 × 10⁹ coccolith g⁻¹ (Fig. 3, Fig. 6), are of similar or higher magnitude than those documented in the Alboran Sea during periods of enhanced primary productivity, such as the Holocene (e.g. Colmenero-Hidalgo et al., 2004; Ausín et al., 2015a,b). Thus, it can be concluded that MIS 11 was a period of high coccolithophore primary productivity, most likely owing to the complete development of the Alboran Upwelling System (Fig. 6c). This

Conclusions

Variations in the primary productivity proxy (PPP) and percentages of small Gephyrocapsa trace the changes in the coccolithophore paleoproductivity, triggered by the variations in the state of activation of the Alboran Upwelling System during the MIS 12/MIS 11 transition and MIS 11. A two-phase atmospheric scenario linked with the intensity of meridional atmospheric pressure gradients, NAO-like, is proposed to explain the changes in the state of activation of the Alboran Upwelling System:

Author statement

Coccolithophore sample analysis was made by AGL. Phytolith sample analysis was made by MAB. IC performed the isotopic analyses. JOG and AC processed and analysed the biomarkers for SST reconstruction. AGL integrated the data and conducted the research with the supervision of JAF. DO, ARH, MM, PM and LAA provided resources. AGL visualized and wrote the paper with the supervision of JAF and FJS and the input of coauthors. Founding acquisition leading to this publication was achieved by FJS and

Data statement

All data used in this study are available in the public repository PANGAEA® as: González-Lanchas, Alba; Flores, José-Abel; Sierro, Francisco J.; Bárcena, María Ángeles; Cortina, Aleix; Cacho, Isabel; Grimalt, Joan O (2020): Nannofossil, opal phytolith, stable isotopes and U^k'₃₇ Sea Surface Temperature record from ODP Site 977 during the MIS 11 https://doi.org/10.1594/PANGAEA.921235.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the FPU contract of the Ministry of Education and Professional Formation of the Spanish government [FPU17/03349] awarded to A. González-Lanchas and by the financing infrastructure provided by the programs of the Ministry of Economy and Competitiveness [CGL 2015-68459-P] and the Ministry of Science, Innovation and Universities [RTI 2018-099489-B-100] granted to the GGO (Grupo de Geociencias Oceánicas) of the University of Salamanca. DO acknowledges funding from

References (131)

F.O. Amore et al.
A middle Pleistocene northeast atlantic coccolithophore record: paleoclimatology and paleoproductivity aspects
Mar. Micropaleontol.
(2012)
B. Ausín et al.
Coccolithophore productivity and surface water dynamics in the Alboran Sea during the last 25 kyr
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2015)
M.A. Bárcena et al.
Evidence of a high-productivity area off the coast of Málaga from studies of diatoms in surface sediments
Mar. Micropaleontol.
(1998)
M. Bárcena et al.
Paleoproductivity variations related to climatic conditions in the Alboran Sea (western Mediterranean) during the last glacial–interglacial transition: the diatom record
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2001)
M. Bárcena et al.
Planktonic response to main oceanographic changes in the Alboran Sea (Western Mediterranean) as documented in sediment traps and surface sediments
Mar. Micropaleontol.
(2004)
S. Barker et al.
Globally increased pelagic carbonate production during the Mid-Brunhes dissolution interval and the CO2 paradox of MIS 11
Quat. Sci. Rev.
(2006)
P. Bazzicalupo et al.
High-frequency climate fluctuations over the last deglaciation in the Alboran Sea, Western Mediterranean: evidence from calcareous plankton assemblages
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2018)
A. Berger et al.
Insolation values for the climate of the last 10 million years
Quat. Sci. Rev.
(1991)
B. Boeckel et al.
Distribution of coccoliths in surface sediments of the south-eastern South Atlantic Ocean: ecology, preservation and carbonate contribution
Mar. Micropaleontol.
(2004)
I. Cacho et al.
Evidence for enhanced Mediterranean thermohaline circulation during rapid climatic coolings
Earth Planet Sci. Lett.
(2000)

I. Candy et al.

Marine Isotope Stage 11: palaeoclimates, palaeoenvironments and its role as an analogue for the current interglacial

Earth Sci. Rev.

(2014)

E. Colmenero-Hidalgo et al.

Ocean surface water response to short-term climate changes revealed by coccolithophores from the Gulf of Cadiz (NE Atlantic) and Alboran Sea (W Mediterranean)

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2004)

T.B. Coplen

New guidelines for reporting stable hydrogen, carbon, and oxygen isotope-ratio data

Geochem. Cosmochim. Acta

(1996)

S. Desprat et al.

Climate variability of the last five isotopic interglacials: direct land-sea-ice correlation from the multiproxy analysis of North-Western Iberian margin deep-sea cores

A.W. Droxler et al.

Marine Isotope Stage 11 (MIS 11): new insights for a warm future

Global Planet. Change

(2000)

L. Fenoglio-Marc et al.

Decadal variability of net water flux at the Mediterranean Sea Gibraltar Strait

Global Planet. Change

(2013)

J.A. Flores et al.

Ocean-surface and wind dynamics in the atlantic ocean off northwest Africa during the last 140 000 years

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2000)

J.A. Flores et al.

Pleistocene calcareous nannofossil stratigraphy for ODP leg 177 (atlantic sector of the southern ocean)

Mar. Micropaleontol.

(2002)

S. Gartner

Paleoceanography of the mid-Pleistocene

Mar. Micropaleontol.

(1988)

J. Giraudeau

Distribution of recent nannofossils beneath the Benguela system: southwest African continental margin

Mar. Geol.

(1992)

A. Girone et al.

Calcareous plankton response to orbital and millennial-scale climate changes across the Middle Pleistocene in the western Mediterranean

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2013)

I. Hernández-Almeida et al.

Microplankton response to environmental conditions in the Alboran Sea (Western Mediterranean): one year sediment trap record

Mar. Micropaleontol.

(2011)

D.A. Hodell et al.

Comparison of interglacial stages in the South Atlantic sector of the southern ocean for the past 450 kyr: implifications for Marine Isotope Stage (MIS) 11

Global Planet. Change

(2000)

J. Johnson et al.

A fine resolution model of the eastern North Atlantic between the Azores, the canary islands and the Gibraltar strait

Deep Sea Res. Oceanogr. Res. Pap.

(2000)

E.S. Kandiano et al.

The meridional temperature gradient in the eastern North Atlantic during MIS 11 and its link to the ocean–atmosphere system

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2012)

M. Knappertsbusch

Geographic distribution of living and holocene coccolithophores in the Mediterranean Sea

Mar. Micropaleontol.

(1993)

A. Koutsodendris et al.

Vegetation dynamics and climate variability during the Holsteinian interglacial based on a pollen record from Dethlingen (northern Germany)

Quat. Sci. Rev.

(2010)

A. Koutsodendris et al.

A short-term climate oscillation during the Holsteinian interglacial (MIS 11c): an analogy to the 8.2ka climatic event?

Glob. Planet. Change

(2012)

M.-F. Loutre et al.

Marine Isotope Stage 11 as an analogue for the present interglacial

Global Planet. Change

(2003)

P. Maiorano et al.

Coccolithophore variability from the shackleton site (IODP site U1385) through MIS 16-10

Global Planet. Change

(2015)

M. Marino et al.

Calcareous plankton and the mid-Brunhes climate variability in the Alboran Sea (ODP Site 977)

Palaeogeogr. Palaeoclimatol. Palaeoecol.

(2018)

C. Millot

Circulation in the western Mediterranean Sea

J. Mar. Syst.

(1999)

A. Moreno et al.

Saharan dust transport and high-latitude glacial climatic variability: the Alboran Sea record

Quat. Res.

(2002)

P.J. Müller et al.

Calibration of the alkenone paleotemperature index U37K′ based on core-tops from the eastern South Atlantic and the global ocean (60° N-60° S)

Geochimica et Cosmochimica Acta

(1998)

D. Oliveira et al.

The complexity of millennial-scale variability in southwestern Europe during MIS 11

Quat. Res.

(2016)

S.L. Olson et al.

A sustained +21m sea-level highstand during MIS 11 (400ka): direct fossil and sedimentary evidence from Bermuda

Quat. Sci. Rev.

(2009)

T.T. Packard et al.

formation of the alboran oxygen minimum zone. Deep sea research Part A

Oceanographic Research Papers

(1988)

M. Pérez-Folgado et al.

WesternMediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr

Mar. Micropaleontol.

(2003)

L.B. Railsback et al.

An optimized scheme of lettered marine isotope substages for the last 1.0 million years, and the climatostratigraphic nature of isotope stages and substages

Quat. Sci. Rev.

(2015)

D.L. Roberts et al.

Melting ice sheets 400,000 yr ago raised sea level by 13 m: Past analogue for future trends

Earth Planet Sci. Lett.

(2012)

R.B. Alley et al.

Holocene climatic instability: A prominent, widespread event 8200 yr ago

Geology

(1997)

M.C. Álvarez et al.

Coccolithophore biogeography in the Mediterranean Iberian margin

Revista Española de Micropaleontología

(2010)

B. Ausín et al.

Atmospheric patterns driving holocene productivity in the Alboran Sea (western mediterranean): a multiproxy approach

Holocene

(2015)

R. Barber et al.

A rising tide lifts all phytoplankton: growth response of other phytoplankton taxa in diatom-dominated blooms

Global Biogeochem. Cycles

(2006)

S. Barker et al.

Icebergs not the trigger for North Atlantic cold events

Nature

(2015)

H.A. Bauch et al.

Contrasting ocean changes between the subpolar and polar North Atlantic during the past 135 ka

Geophys. Res. Lett.

(2012)

K.-H. Baumann et al.

The significance of extant coccolithophores as indicators of ocean water masses, surface water temperature, and palaeoproductivity: a review

Paläontol. Z.

(2005)

K.-H. Baumann et al.

Coccolith Contribution to South Atlantic Carbonate Sedimentation, Coccolithophores

(2004)

P. Bazzicalupo et al.

Holocene climate variability of the Western Mediterranean: surface water dynamics inferred from calcareous plankton assemblages

Holocene

(2020)

W. Berger et al.

On the dynamics of the ice ages: stage-11 paradox, mid-Brunhes climate shift, and 100-ky cycle

GEOPHYSICAL MONOGRAPH-AMERICAN GEOPHYSICAL UNION

(2003)

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A centennial scale study has been performed on the coccolith assemblage of the Integrated Ocean Drilling Program Site U1390 in the Gulf of Cadiz in order to identify changes in the surface water dynamics during the last 20 kyr. The dataset is integrated with selected planktonic foraminifer taxa and with available sedimentary and paleoceanographic proxies. The reconstructed surface water conditions controlling coccolithophores shifted from a prevailing influence of Portugal Current during the Last Glacial Maximum, to enhanced advection of subtropical water during the Holocene. Millennial to centennial-scale fluctuations are also well recorded based on abundance fluctuations of key coccolithophore taxa. During Heinrich Stadial 1 and Younger Dryas, wind/frontal-induced upwelling favored nutrient availability and productivity in surface waters, although colder temperatures during Heinrich Stadial 1 inhibited coccolithophore proliferation. Combining calcareous plankton and oxygen isotope data it was possible to highlight that Heinrich Stadial 1 has an internal variability, marked by three distinct phases. Cold and productive surface water conditions occurring during HS1a and HS1c were interrupted during HS1b by enhanced influence of the warm Azores Current at the core location, which acted in phase with increased Mediterranean Outflow Water strength. The sharpest abundance of the polar-subpolar/melt-water related taxa, observed during HS1c, suggests this was the most extreme cold climate phase in the Gulf of Cadiz during the last 20 kyr. During the Bølling-Allerød interstadial, the northward extension of the subtropical gyre, coupled with enhanced fluvial discharge, determined the increase of warm water taxa and Emiliania huxleyi large morphotype, which was able to adapt to less saline waters. During the Holocene, mainly during the last 8 kyr, over the main warming trend, coccolith assemblages display short-term fluctuations. The N ratio index together with the pattern of Gephyrocapsa oceanica, compared with a palaeo record of NAO, indicates that centennial-scale events of enhanced mixing are in phase with more arid conditions on land. This pattern is related with periods of (+) North Atlantic Oscillation leading to a prevalence of strong northerly winds and enhanced mixing during the winter season.
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The surface-water stratification linked to the arrival of cold and less saline polar water in the Gulf of Cadiz reduced the coccolithophores assemblages during these short time intervals. The same paleoenvironmental conditions were observed during the last glacial cycle in the Gulf of Cadiz by Voelker et al. (2009), during the Middle Pleistocene at Site U1313 (Cavaliero et al., 2018), on the Iberian Margin (Cavaleiro et al., 2020; Gonzalez-Lanchas et al., 2021), in the Alboran Sea (González-Lanchas et al., 2020), and on the Iberian Margin during the last 28 kyr (Ausín et al., 2020), the last 700 kyr (Incarbona et al., 2010), and the last 150 kyr (Pailler and Bard, 2002; Salgueiro et al., 2010) as well as in the present day in the Norwegian-Greenland Sea (Baumann et al., 2000). However, conflicting data exist on the productivity effects during abrupt climatic events along the Iberian Margin (Ausín et al., 2020), showing productivity increases during melting phases (Eynaud et al., 2000; Lebreiro et al., 1997; Thomson et al., 2000).
Coccolithophore high resolution (300 years) quantitative analyses have been carried out on Early Pleistocene sediment samples from Integrated Ocean Drilling Program Site U1387 retrieved in the Gulf of Cadiz. The studied interval is well constrained by the δ¹⁸O chronological frame and covers marine isotope stage (MIS) 48 to MIS 45, from 1465.9 ka to 1389.9 ka. The aim is to investigate paleoenvironmental changes during a poorly known interval of the “41 ky world” and understand how climate dynamics controlled coccolithophore abundance and variation at orbital up to millennial scale. Assemblage composition variation and Principal Component Analysis (PCA) indicate that temperature and nutrient availability are the main factors influencing coccolithophores. Precession forcing combined with hydrological and atmospheric dynamics affect changes in coccolithophore assemblage composition and abundance highlighting glacial-interglacial cycles and a millennial scale variability, which is more evident during glacials than during interglacials. Interglacial MIS 47 onset is more abrupt than MIS 45 inception in relation to a more prominent insolation maximum, which favors the sharp increase and highest abundance of warm water taxa in the early MIS 47. Short-term abundance peaks of C. pelagicus spp. pelagicus during glacials document polar-subpolar melting water influx into the Gulf of Cadiz and southward migration of the subpolar front during episodes of high volume ice-sheet in the north hemisphere and reduced Atlantic Meridional Overturning circulation. In late MIS 48 the lowest coccolithophore productivity, induced by colder and stratified surface waters, a terminal stadial has been inferred. Enhanced short-term glacial productivity is favored by higher mixing and nutrient content in surface water due to the strengthened westerly winds during +NAO-like phases. This promotes arid condition and upwelling along the studied site. The interglacial short-term coccolithophore productivity increases are associated with insolation maxima and enhanced nutrients of land origin during more humid periods led by -NAO-like phases, which induce the southward position of the westerlies and higher precipitation in the Mediterranean region and North Africa, in agreement with the contemporary sapropel occurrences in Mediterranean Sea. Our data-set suggests a connection between climate dynamics in the Gulf of Cadiz and east of Gibraltar Strait during the Early Pleistocene as well as a relationship with the north hemisphere ice-sheet dynamics.
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Citation Excerpt :
After considering the densities and linear sedimentation rates, the nannofossil accumulation rates (NARs; coccoliths cm−2 ka−1) were estimated. The total NAR values can be used as a proxy for coccolithophore productivity (Flores et al., 2003; González-Lanchas et al., 2020; Imai et al., 2015). In addition to the total NAR, the relative abundance (%) and NAR of the most abundant taxa were calculated.
Calcareous nannofossil assemblages and fragmentation ratios of two coccolithophore species (Coccolithus pelagicus and Calcidiscus leptoporus) were analysed in samples from ODP Site 1090, South Atlantic (42° 54.8′S, 8° 53.9′E), to obtain valuable insights into the paleoceanographic evolution and carbonate preservation trends during the late Pliocene and Early Pleistocene (3.14–1.80 Ma). Coccolithophore species were identified in a total of 232 samples. Calcareous nannofossil counts revealed shifts in the assemblages that can be correlated with the climatic evolution of the Southern Ocean. Between 3.2 and 2.85 Ma, i.e. during the mid-Pliocene Warmth, the assemblage was dominated by small Gephyrocapsa, a group of species typically associated with upwelling conditions. The dominance of the opportunistic small Gephyrocapsa group can be linked to a more intense mixing of the upper water column most likely due to the more southward position of the Subtropical Front (STF) compared with its present position. After 2.85 Ma, a gradual increase in the cold water species C. pelagicus marked a progressive cooling of the South Atlantic coupled with a northward shift of the (STF). The changes in the assemblage composition co-varied with the δ¹⁸O record. Periods with isotopically heavier values (glacial) were dominated by C. pelagicus and periods with lighter values (interglacial) were dominated by very small reticulofenestrids (VSR; <3 μm). After 2.7 Ma, an intensification of the glacial-interglacial patterns of C. pelagicus and VSR was registered. The interval between 2.44 and 2.34 Ma was characterised by low abundance of C. pelagicus and higher biodiversity which are interpreted to be due to a temporal southward movement of the STF interrupting the previously registered cooling. After 2.0 Ma, the decreasing abundance of C. pelagicus suggests a slowdown of the relatively intense cooling registered since 2.7 Ma. The fragmentation ratios of C. pelagicus and C. leptoporus suggest moderate preservation along our interval, with a general trend toward better preservation after 2.2 Ma. This enhanced preservation has been related to a greater input of the less-corrosive northern component water mass into the Cape Basin after 2.2 Ma. The lack of significant glacial-interglacial variations in the fragmentation ratios suggests that the low amplitude of the glacial cycles did not have a substantial impact on the carbonate preservation throughout the entire interval. During MIS 99–98 (approximately 2.5 Ma), a remarkably high accumulation of VSR was found and identified as a short (9 ka) event of high productivity. The timing of this event coincides with that of the Eltanin impact (approximately 2.5 Ma), suggesting that, albeit speculatively, the two events may be related.
Trace fossil characterization during Termination V and MIS 11 at the western Mediterranean: Connection between surface conditions and deep environment
2022, Marine Geology
Citation Excerpt :
Suborbital-scale instabilities associated with the southward incursion of waters with an Arctic origin (Oppo et al., 1998) are comparatively well recorded towards the late MIS 11 (~ 395–374 kyr), as Heinrich-type (Ht) events at Iberian latitudes (de Abreu et al., 2005; Hodell et al., 2013; Martrat et al., 2007; Palumbo et al., 2013; Rodrigues et al., 2011; Stein et al., 2009; Voelker et al., 2010). In the Alboran Sea, such climate changes have been recognized from high-resolution coccolithophore records and suggested to impact the conditions of WMDW formation and western Mediterranean thermohaline circulation, responsible of differential stimulation of the Alboran Upwelling System and regional primary productivity (González-lanchas et al., 2020). Given this preamble and the general intense dynamic behavior of the surface systems and primary production in this region (Bárcena et al., 2004; Hernández-Almeida et al., 2011), it seems consistent to expect such a dynamical response recorded in the deep environmental levels, where trace makers inhabits.
Trace fossil assemblages are studied at Ocean Discovery Program (ODP) Site 977 to characterize the response of the macrobenthic trace maker community to deep paleoenvironmental conditions during the Termination V (TV) and interglacial Marine Isotope Stage (MIS) 11 at the western Mediterranean Alboran Sea. An assemblage composed of Chondrites, Planolites, Scolicia, Thalassinoides and Zoophycos is identified, showing notable variations in ichnodiversity, abundance and Bioturbation Index, that were analyzed in detail. The integration of ichnological information with sediment color and high-resolution coccolithophore records from Site 977, evidenced that variations in macrobenthic trace maker community are primarily controlled by oxygen availability and surface organic productivity patterns. During TV, high surface organic productivity by intense Alboran Upwelling System enhanced the deep organic accumulation that, together with reduced deep-water removal, resulted in a decrease of bioturbation and the formation of an Organic Rich Layer. Moderate and stable surface production through MIS 11c reduced deep food availability, resulting in an oligotrophic and stable deep environment. This is reflected by relatively abundant trace fossils in lighter sediments. Intra-interglacial increase in surface organic production at ~405 ka is evidenced by increased organic matter preservation. Minor impact of western Mediterranean circulation on deep-water removal, but a plausible stronger control by Bernoulli aspiration intensities in the region, is, in overall, observed during these intervals. During the Heinrich-type (Ht) events 3 and 2, increased trace fossil diversity and ameliorated oxygenation is driven by limited surface organic production, but intense western Mediterranean deep-water circulation and enhanced regional deep-water removal.
Meltwater flux from northern ice-sheets to the mediterranean during MIS 12
2021, Quaternary Science Reviews
Citation Excerpt :
Based on this assumption, we built an age model for ODP Site 977 by aligning its alkenone-based SST record (extended from González-Lanchas et al., 2020) to that of the north Atlantic mid-latitude record IODP Site U1313 (Naafs et al., 2011; Stein et al., 2009) (Fig. 2). Two primary control points for MIS 12 were added to extend the age model of González-Lanchas et al. (2020). The existing KC01B age model was elaborated through the tuning of sapropels with the astronomical records (Capotondi et al., 2016; Konijnendijk et al., 2014; Lourens, 2004).
Planktonic foraminifer oxygen isotopes through MIS 12 were analysed from Ocean Drilling Program Site 977 in the Alboran Sea. After the correction of the sea surface temperature (SST) effect on the δ¹⁸O composition of foraminiferal calcite, the resulting seawater δ¹⁸O (δ¹⁸O_w) was used to reconstruct variations in the δ¹⁸O_w of the Atlantic inflow into the Mediterranean. A synchronous record from the KC01B core, in the Ionian Sea, was used to evaluate changes in the oxygen isotope gradient within the Mediterranean due to hydrological variations during MIS 12. Instead of the glacial δ¹⁸O_w enrichment expected for the Mediterranean, lower values than today have been observed both in the Alboran and the Ionian seas, especially between 455 ka and the end of MIS 12 (424 ka). These negative oxygen isotope anomalies must have been caused by a flux of freshwater to the Mediterranean during MIS 12. Although the largest fraction of the freshwater anomalies entered the Mediterranean through the Atlantic inflow, especially during Heinrich stadials, the Mediterranean δ¹⁸O_w gradient allowed us to identify other sources of freshwater to the eastern basin. One of these sources was probably the meltwater generated at the southern margin of the Fennoscandian ice-sheet that entered via the Caspian and Black seas. However, the proximity of core KC01B to the Adriatic Sea points to meltwater delivered from the Alpine ice-sheet and transported through the Po river into the Mediterranean as the main cause of the Ionian Sea ¹⁸O depletions.

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