Holocene evolution of the North Atlantic subsurface transport

Repschläger, Janne; Garbe‐Schönberg, Dieter; Weinelt, Mara; Schneider, Robert

doi:10.5194/cp-13-333-2017

Cited by 40 publications

(81 citation statements)

References 62 publications

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“…Cacho et al, 2001;NGRIP-Members, 2004), thus corroborating warmer SSTs during the mid-Holocene compared to modern SSTs. Annual mean SST values around 19 • C at that time were also reconstructed by other studies from the Alboran Sea (Ausín et al, 2015;Cacho et al, 2001;Martrat et al, 2014;Pérez-Folgado et al, 2003;Rodrigo-Gámiz et al, 2014). Moreover, Cacho et al (2001) described a cold SST event of about 1.5 • C in the Alboran Sea between 5.94 and 4.75 ka cal BP.…”

Section: Hydrological Conditions In the Gulf Of Cádiz And The Alboransupporting

confidence: 72%

Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

et al. 2019

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Abstract. To assess the regional multi-decadal to multi-centennial climate variability along the southern Iberian Peninsula during the mid- to late-Holocene record of paleo-environmental indicators from marine sediments were established for two sites in the Alboran Sea (ODP-161-976A) and the Gulf of Cádiz (GeoB5901-2). High-resolution records of organic geochemical properties and planktic foraminiferal assemblages are used to decipher precipitation and vegetation changes as well as hydrological conditions with respect to sea surface temperature (SST) and marine primary productivity (MPP). As a proxy for precipitation change, records of plant-derived n-alkane composition suggest a series of five distinct dry episodes in southern Iberia at 5.4±0.3 ka cal BP, from 5.1 to 4.9±0.1 ka cal BP, from 4.8 to 4.7±0.1 ka cal BP, from 4.4 to 4.3±0.1 ka cal BP, and at 3.7±0.1 ka cal BP. During each dry episode the vegetation suffered from reduced water availability. Interestingly, the dry phase from 4.4 to 4.3±0.1 ka cal BP is followed by a rapid shift towards wetter conditions revealing a more complex pattern in terms of its timing and duration than was described for the 4.2 ka event in other regions. The series of dry episodes as well as closely connected hydrological variability in the Alboran Sea were probably driven by NAO-like (North Atlantic Oscillation) variability. In contrast, surface waters in the Gulf of Cádiz appear to have responded more directly to North Atlantic cooling associated with Bond events. In particular, during Bond events 3 and 4, a pronounced increase in seasonality with summer warming and winter cooling is found.

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Section: Hydrological Conditions In the Gulf Of Cádiz And The Alboransupporting

confidence: 72%

Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

et al. 2019

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“…Recently, a gradual northward shift in the position of the Azores Front during the mid-Holocene was proposed (Repschläger et al, 2017). This pattern is similar to a positive winter NAO-like state from~8.7 to 4 Kyr BP (Figure 2b).…”

Section: Temporospatial Patterns Of Climate At~31°n In Nw Africasupporting

confidence: 59%

“…The high value corresponds to a more northward shift of the Azores Front(Repschläger et al, 2017). (b) Position of the Azores Front based on the abundance of the planktonic foraminifera Globigerinoides ruber (G. ruber W.) in the sediment core in the vicinity of the Azores.…”

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confidence: 99%

How Far North Did the African Monsoon Fringe Expand During the African Humid Period? Insights From Southwest Moroccan Speleothems

Sha

Brahim

Wassenburg

et al. 2019

Geophysical Research Letters

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We present new high-resolution oxygen isotope (δ 18 O) records from three NW African speleothems located at~31°N. The present-day rainfall patterns at 31°N in NW Africa are linked to negative winter North Atlantic Oscillation phases. However, on multimillennial time scales, our δ 18 O records, together with other hydroclimate records, provide new evidence of humid conditions during the mid-Holocene, a period that was presumably characterized by arid climate. Thus, the apparent increase in moisture during the mid-Holocene is interpreted better as an increase in summer rainfall. This is most likely linked to the expansion of the West African summer monsoon fringe during the African Humid Period, which terminated in our record abruptly around 4 Kyr BP. The temporospatial difference with speleothem records from N Morocco suggests that the High-Atlas Mountains might have been a topographic barrier to further expansion of the West African summer monsoon fringe into higher latitudes. Plain Language SummaryThe Holocene African Humid Period in North Africa, characterized by the expansion of vegetation into the Green Sahara, has been linked to the intensification of the West African summer monsoon (WASM). However, the temporospatial pattern of the African Humid Period, especially the northernmost expansion of the WASM, remain a matter of controversy, largely owing to the lack of precisely dated and high-resolution paleoclimatic records. This study presents new highresolution paleoclimate data based on speleothem oxygen isotope records from a key site at~31°N in NW Africa. Our data suggest that the WASM expanded to 31°N in NW Africa during the mid-Holocene and terminated abruptly at 4 Kyr BP.

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“…In order to provide a detailed overview of the linkage between the Western Mediterranean rainfall and the ice-rafting on a centennial to millennial timescale, we compare our data with paleo-oceanographic and atmospheric reconstructions of the North Atlantic region. These include a record of the position of the AF and the extent of the subtropical gyre (STG; Repschläger et al, 2017; Figure 3d), a record of the activity of the subpolar gyre (SPG; Thornalley et al, 2009; Figure 3c) and a recent reconstruction of storminess from Western Denmark reflecting periods of enhanced northerly shifts of the westerly winds belt (akin to positive NAO; Figure 3b; Goslin et al, 2018).…”

Section: North Atlantic Ocean and Atmospheric Dynamics During The Irdmentioning

confidence: 99%

“…(c) North Atlantic current activity, expressed by the activity of the subpolar gyre (SPG) based on the water-column density-difference (Thornalley et al, 2009). (d) Position of the AF and the extent of the subtropical gyre, based on the abundance of the planktonic foraminifera Globigerinoides ruber (G. ruber w.) in a sediment core in the vicinity of the Azores (Repschläger et al, 2017). (e) Detrended rainfall index of the Western Mediterranean, derived from speleothem δ 18 O records (Cha1, Cha2, and GP2) from Northern Morocco.…”

Section: North Atlantic Ocean and Atmospheric Dynamics During The Irdmentioning

confidence: 99%

North Atlantic Ice‐Rafting, Ocean and Atmospheric Circulation During the Holocene: Insights From Western Mediterranean Speleothems

Brahim

Wassenburg

Sha

et al. 2019

Geophysical Research Letters

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In this study, we present a Holocene rainfall index based on three high‐resolution speleothem records from the Western Mediterranean, a region under the influence of the westerly winds belt modulated by the North Atlantic Oscillation (NAO). On centennial to millennial timescales, we show that the North Atlantic ice‐rafting events were likely associated with negative NAO‐like conditions during the Early Holocene and the Late Holocene. However, our data reveal that this is not clearly the case for the mid‐Holocene ice‐rafting events, during which we also show evidence of positive NAO‐like patterns from other paleo‐oceanographic and paleo‐atmospheric data. Hence, contradictory mechanisms involving prolonged periods of both north and south shifts of the westerly winds belt (resembling positive and negative NAO‐like patterns) might at least partially trigger or amplify the ice‐rafting events and the slowdown of the Atlantic Meridional Overturning Circulation.

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Holocene evolution of the North Atlantic subsurface transport

Cited by 40 publications

References 62 publications

Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

Multi-decadal atmospheric and marine climate variability in southern Iberia during the mid- to late-Holocene

How Far North Did the African Monsoon Fringe Expand During the African Humid Period? Insights From Southwest Moroccan Speleothems

North Atlantic Ice‐Rafting, Ocean and Atmospheric Circulation During the Holocene: Insights From Western Mediterranean Speleothems

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