Eccentricity-induced expansions of Brazilian coastal upwelling zones

Lessa, Douglas Villela de Oliveira; Santos, Thiago Pereira dos; Venancio, Igor Martins; Santarosa, Ana Cláudia Aoki; Junior, Edmundo C. dos Santos; Toledo, Felipe Antonio de Lima; Costa, Karen Badaraco; Albuquerque, Ana Luíza Spadano

doi:10.1016/j.gloplacha.2019.05.002

Cited by 18 publications

(50 citation statements)

References 70 publications

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“…As discussed before, marine productivity caused by upwelling on the shelf of Cabo Frio was apparently of minor importance. Based on planktic foraminiferal assemblages (Lessa et al, 2019), enhanced upwelling occurred between HSs 3 and 4 at around 35 ka, when a small peak of CWC abundances occurs (Fig. 5g).…”

Section: Cwcs At Bowie Mound In the Paleoclimatological Contextmentioning

confidence: 99%

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

et al. 2020

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Abstract. Cold-water corals (CWCs) constitute important deep-water ecosystems that are under increasing environmental pressure due to ocean acidification and global warming. The sensitivity of these deep-water ecosystems to environmental change is demonstrated by abundant paleorecords drilled through CWC mounds that reveal characteristic alterations between rapid formation and dormant or erosive phases. Previous studies have identified several central parameters for driving or inhibiting CWC growth such as food supply, oxygenation, and the carbon saturation state of bottom water, yet there are still large uncertainties about the relative importance of the different environmental parameters. To advance this debate we have performed a multiproxy study on a sediment core retrieved from the 25 m high Bowie Mound, located at 866 m water depth on the continental slope off southeastern Brazil, a structure built up mainly by the CWC Solenosmilia variabilis. Our results indicate a multifactorial control on CWC growth at Bowie Mound during the past ∼ 160 kyr, which reveals distinct formation pulses during northern high-latitude glacial cold events (Heinrich stadials, HSs) largely associated with anomalously strong monsoonal rainfall over the continent. The ensuing enhanced runoff elevated the terrigenous nutrient and organic-matter supply to the continental margin and likely boosted marine productivity. The dispersal of food particles towards the CWC colonies during HSs was facilitated by the highly dynamic hydraulic conditions along the continental slope that prevailed throughout glacial periods. These conditions caused the emplacement of a pronounced nepheloid layer above Bowie Mound, thereby aiding the concentration and along-slope dispersal of organic matter. Our study thus emphasizes the impact of continental climate variability on a highly vulnerable deep-marine ecosystem.

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Section: Cwcs At Bowie Mound In the Paleoclimatological Contextmentioning

confidence: 99%

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

et al. 2020

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“…Records were placed on a common timescale (RJ-1501), and the means around zero were subtracted (RJ-1502 minus RJ-1501) to produce alkenone (U K 37 )-derived sea surface temperature (SST) and δ-ice-volume free seawater oxygen isotope ( δ 18 O IVF−SW ). The records were bootstrapped using the Acycle software with a 10 % window (Li et al, 2019) and presented with the 2.5th and 97.5th percentiles (red and blue shaded areas). (a) δU K 37 -derived SST.…”

Section: Discussionmentioning

confidence: 99%

“…Those cores located adjacent to the semiarid NE Brazil allowed several investigations addressing the interplay between changes in the Atlantic Meridional Overturning Circulation (AMOC), the sea surface temperature (SST) of the tropical Atlantic, and the continental climate (in terms of precipitation and vegetation cover) in centennial to millennial timescales (Behling et al, 2000;Bouimetarhan et al, 2018;Burckel et al, 2015;Crivellari et al, 2019;Venancio et al, 2018;Zhang et al, 2015Zhang et al, , 2017. Otherwise, marine records recovered from the subtropical realm (south of 20 • S) generally do not show obvious sea surface millennial-scale features like those from NE Brazil (Santos et al, 2017a); nonetheless, this area suffers large changes in the winddriven upwelling patterns, with consequences for regional upper-ocean productivity (Lessa et al, 2019;Portilho-Ramos et al, 2019). The subtropical Brazilian margin may also be a sensitive region to the transmission of the Agulhas rings to the western South Atlantic at the end of glacial periods, highlighting its importance for glacial-interglacial transitions (Santos et al, 2017b;Ballalai et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

Luz

Santos

Eglinton³

et al. 2020

Clim. Past

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Abstract. The number of sedimentary records collected along the Brazilian continental margin has increased significantly in recent years, but relatively few are located in shallow waters and register paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instance, the northward flow up to 23–24∘ S of cold and fresh shelf waters sourced from the Subantarctic region is an important feature of current hydrodynamics in the subtropical western South Atlantic Ocean, and yet limited information is available for the long-term changes of this system. Herein, we considered a suite of organic and inorganic proxies – alkenones-derived sea surface temperature (SST), δD-alkenones, δ18O of planktonic foraminifera, and ice-volume free seawater δ18OIVF−SW – in sediment from two cores (RJ-1501 and RJ-1502) collected off the Rio de Janeiro Shelf (SE Brazilian continental shelf) to shed light on SST patterns and relative salinity variations since the end of the last glacial cycle in the region and the implications of these processes over a broader spatial scale. The data indicate that, despite the proximity (∼40 km apart) of both cores, apparently contradictory climatic evolution occurred at the two sites, with the shallower (deeper) core RJ-1501 (RJ-1502) showing consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum (LGM) and last deglaciation. This can be reconciled by considering that the RJ-1501 core registered a signal from mid- to high latitudes on the upper slope off Rio de Janeiro represented by the influence of the cold and fresh waters composed of Subantarctic Shelf Water and La Plata Plume Water transported northward by the Brazilian Coastal Current (BCC). The data from core RJ-1502 and previous information for deep-cores from the same region support this interpretation. In addition, alkenone-derived SST and δ18OIVF−SW suggest a steep thermal and density gradient formed between the BCC and Brazil Current (BC) during the last climate transition which, in turn, may have generated perturbations in the air–sea heat flux with consequences for the regional climate of SE South America. In a scenario of future weakening of the Atlantic Meridional Overturning Circulation, the reconstructed gradient may become a prominent feature of the region.

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“…Marine records recovered from the subtropical realm (southern to 20 ºS) generally do not show obvious surface millennialscale features like those from NE Brazil (Santos et al, 2017a); nonetheless, this area suffers significant changes in wind-driven upwelling patterns, with consequences for regional upper-ocean productivity (Lessa et al, 2019;Portilho-Ramos et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

Luz¹,

Santos²,

Eglinton³

et al. 2020

Preprint

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Eccentricity-induced expansions of Brazilian coastal upwelling zones

Cited by 18 publications

References 70 publications

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

Monsoonal forcing of cold-water coral growth off southeastern Brazil during the past 160 kyr

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

Contrasting late-glacial paleoceanographic evolution between the upper and lower continental slope of the western South Atlantic

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