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

Abstract

Temporal and spatial patterns in eastern North Atlantic sea-surface temperatures (SST) were reconstructed for marine isotope stage (MIS) 11c using a submeridional transect of five sediment cores. The SST reconstructions are based on planktic foraminiferal abundances and alkenone indices, and are supported by benthic and planktic stable isotope measurements, as well as by ice-rafted debris content in polar and middle latitudes. Additionally, the larger-scale dynamics of the precipitation regime over northern Africa and the western Mediterranean region was evaluated from iron concentrations in marine sediments off NW Africa and planktic δ 13 C in combination with analysis of planktic foraminiferal abundances down to the species level in the Mediterranean Sea. Compared to the modern situation, it is revealed that during entire MIS 11c sensu stricto (ss), i.e., between 420 and 398 ka according to our age models, a cold SST anomaly in the Nordic seas co-existed with a warm SST anomaly in the middle latitudes and the subtropics, resulting in steeper meridional SST gradients than during the Holocene. Such a SST pattern correlates well with a prevalence of a negative mode of the modern North Atlantic Oscillation. We suggest that our scenario might partly explain the longer duration of wet conditions in the northern Africa during MIS 11c compared to the Holocene.

Coccolithophore variability from the Shackleton Site (IODP Site U1385) through MIS 16-10

“…3c-d) and it is in good agreement with the age of SST increase recorded at the Iberian margin at core MD03-2699 (426.6 ka, Rodrigues et al, 2011), with the wwt group increasing at core MD01-2446(426 ka, Marino et al, 2014, and with several other North Atlantic and continental records (e.g. Oppo et al, 1998;Desprat et al, 2005;de Abreu et al, 2005;Stein et al, 2009;Kandiano et al, 2012). During MIS 11.3 the wwt group depicts a long lasting surface water warming if compared to the other warm phases of previous interglacials.…”

“…3f), which may reflect a new available habitat in stratified waters and well-developed oligotrophic conditions down to the middle of the photic zone. Such a surface water condition could result from continuous and enhanced influence of the subtropical waters at the site during this interval, in agreement with mid-latitude North Atlantic records (de Abreu et al, 2005;Martrat et al, 2007;Helmke et al, 2008;Hagino and Kulhanek, 2009;Stein et al, 2009;Voelker et al, 2010;Rodrigues et al, 2011;Kandiano et al, 2012;Marino et al, 2014). However, we cannot exclude that decreased detrital input from land, resulting from the high sea level stand during MIS 11.3 (Bintanja and van de Wal, 2008), may have also induced both enhanced oligotrophic conditions and minor coccolith dilution (high total N), due to reduced delivery of land-derived nutrients and decreased detrital input, respectively.…”

Global and regional sea surface temperature trends during Marine Isotope Stage 11

“…The apparent later onset of MIS11 optimum and the longer duration of interglacial warmth have been also noted by the authors of the individual records included in our compilation, particularly for records from the North Atlantic region. These authors hypothesized that the persistence of the northern ice sheets throughout MIS11 may have led to a dominant negative mode of the North Atlantic Oscillation (NAO) (Kandiano et al, 2012) whilst the associated sustained meltwater input in the (sub-)polar regions may have resulted in a less stable Atlantic meridional overturning circulation (AMOC; Voelker et al, 2010). In either case, these phenomena would lead to a reduced ocean heat transfer into the North Atlantic, causing a delayed optimum in the SST trends.…”

“…On the other hand, temperatures in the northern high latitudes during MIS11 appear lower than in the Holocene (Bauch et al, 2000;Helmke et al, 2003), and their temporal development seems to deviate from the global trend (Kandiano et al, 2012). These differences have been linked to changes in the strength of the Atlantic meridional overturning circulation, underlining the importance of the response of oceanic circulation to global forcing during Termination V and MIS11 (Dickson et al, 2009;Vázquez Riveiros et al, 2013).…”

The last interglacial (MIS 5e) cycle at Little Bahama Bank: A history of climate and sea-level changes

“…6), arguing for generally colder sea surface conditions. The inferred broad 310 salinity tolerance of this species, also to neritic conditions (Bé and Tolderlund, 1971;Schmuker and Schiebel, 2002), was used in some studies to link high proportions of G. ruber (pink and white varieties) with low surface salinities (Vautravers et al, 2007;Kandiano et al, 2012). The plots of the global distribution pattern of G. ruber (white) and G. ruber (pink), however, suggest that when relative abundances of these two species are approaching maximum values (40% and 10%, respectively), the sea surface salinities would be higher for specimens of the white variety of G. ruber (Hilbrecht, 1996).…”