Late Pliocene upwelling in the Southern Benguela region

Petrick, Benjamin; McClymont, Erin L.; Felder, Sonja; Rueda, Gemma; Leng, Melanie J.; Rosell‐Melé, Antoni

doi:10.1016/j.palaeo.2015.03.042

Cited by 29 publications

(31 citation statements)

References 69 publications

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“…Previous research has demonstrated that even within a single site there can be offsets between proxies which are not continuous through time (e.g. Lawrence and Woodard, 2017;Petrick et al, 2018), so that high-resolution and multi-proxy work is required to fully understand the offhttps://doi.org/10.5194/cp-16-1599-2020…”

Section: Data-model Comparisons For Low-latitude Sitesmentioning

confidence: 99%

Lessons from a high CO2 world: an ocean view from ~3 million years ago

McClymont¹,

Ford

et al. 2020

Preprint

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A range of future climate scenarios are projected for high atmospheric CO2 concentrations, given uncertainties over future human actions as well as potential environmental and climatic feedbacks. The geological record offers an opportunity to understand climate system response to a range of forcings and feedbacks which operate over multiple temporal and spatial scales. Here, we examine a single interglacial during the late Pliocene (KM5c, ca. 3.205 +/- 0.01 Ma) when atmospheric CO2 concentrations were higher than pre-industrial, but similar to today and to the lowest emission scenarios for this century. As orbital forcing and continental configurations were almost identical to today, we are able to focus on equilibrium climate system response to modern and near-future CO2. Using proxy data from 32 sites, we demonstrate that global mean sea-surface temperatures were warmer than pre-industrial, by ~2.3 &#186;C for the combined proxy data (foraminifera Mg/Ca and alkenones), or by ~3.2&#186;C (alkenones only). Compared to the pre-industrial, reduced meridional gradients and enhanced warming in the North Atlantic are consistently reconstructed. There is broad agreement between data and models at the global scale, with regional differences reflecting ocean circulation and/or proxy signals. An uneven distribution of proxy data in time and space does, however, add uncertainty to our anomaly calculations. The reconstructed global mean sea-surface temperature anomaly for KM5c is warmer than all but three of the PlioMIP2 model outputs, and the reconstructed North Atlantic data tend to align with the warmest KM5c model values. &#160;Our results demonstrate that even under low CO2 emission scenarios, surface ocean warming may be expected to exceed model projections, and will be accentuated in the higher latitudes.

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Section: Data-model Comparisons For Low-latitude Sitesmentioning

confidence: 99%

Lessons from a high CO2 world: an ocean view from ~3 million years ago

McClymont¹,

Ford

et al. 2020

Preprint

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“…However, the Pliocene variability of the LC south of the North West Cape remains undocumented to date and the effect of ITF variability on Indian Ocean circulation remains debated. Some authors suggest it as a major factor (Karas et al, ), while others find little influence (Petrick et al, ). To close this gap, we present multiproxy records from Site U1459 (Figure ) detailing oceanographic conditions in the Perth Basin throughout the Pliocene.…”

Section: Introductionmentioning

confidence: 99%

Stepwise Weakening of the Pliocene Leeuwin Current

Vleeschouwer

Petrick

Martínez‐García

2019

Geophysical Research Letters

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The Indonesian Throughflow (ITF) operates as an important link in global thermohaline circulation, and ITF variability probably modulated Pliocene climate change. Yet, whether ITF variability accounted for oceanographic change south of Northwest Cape remains controversial. Here, we present a multiproxy oceanographic reconstruction from the Perth Basin and reconstruct the Pliocene history of the Leeuwin Current (LC). We show that the LC was active throughout the Pliocene, albeit with fluctuations in intensity and scope. Three main factors controlled LC strength. First, a tectonic ITF reorganization caused an abrupt and permanent LC reduction at 3.7 Ma. On shorter timescales, eustatic sea level and direct orbital forcing of wind patterns hampered or promoted the LC. At 3.3 Ma, for instance, LC intensity plunged in response to a eustatic ITF restriction. Site U1459 then fell outside the extent of a weakened LC, and the latitudinal sea surface temperature gradient along West Australia doubled its steepness.

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“…It cannot be definitively proven what process is affecting the high productivity at the site. However, given our current understanding on the South Atlantic oceanic and atmospheric circulation links, the balance of the evidence points to source water from the upwelling zone reaching ODP Site 1087 [ Petrick et al ., ]. MIS 10 was also identified as a particularly cold glacial stage in a site close to (but not in) the Agulhas Current [ Bard and Rickaby , ] (MD96‐2077), whereas the lack of major cooling within the Agulhas Current [ Caley et al ., ] (MD96‐2048) argues against an upstream control over SSTs at ODP Site 1087 (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, the biogeochemical data indicate MAR values similar to the late Pliocene when upwelling water is believed to have affected this site [ Petrick et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Changing surface water conditions for the last 500 ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

et al. 2015

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The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productive Benguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0–500 ka). The UK′37 index and dinoflagellate cyst assemblages are used to reconstruct SSTs, δDalkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The δDalkenone, as a salinity indicator, increases before SSTs, suggesting that the pattern of Agulhas leakage is more complex than suggested by SST proxies. Marine isotope stage (MIS) 10 shows an anomalous pattern: it is marked by a pronounced increase in chlorine concentration, which may be related to enhanced/expanded Benguela upwelling reaching the core site. We find no evidence of an absence of Agulhas leakage throughout the record, suggesting that there is no Agulhas cutoff even during MIS 10. Finally, the ODP Site 1087 record shows an increasing strength of Agulhas leakage towards the present day, which may have impacted the intensity of the Atlantic meridional overturning circulation. As a result, the new analyses from ODP Site 1087 demonstrate a complex interaction between influences of the Benguela upwelling and the Agulhas leakage through the late Pleistocene, which are inferred here to reflect changing circulation patterns in the Southern Ocean and in the atmosphere.

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Late Pliocene upwelling in the Southern Benguela region

Cited by 29 publications

References 69 publications

Lessons from a high CO2 world: an ocean view from ~3 million years ago

Lessons from a high CO2 world: an ocean view from ~3 million years ago

Stepwise Weakening of the Pliocene Leeuwin Current

Changing surface water conditions for the last 500 ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

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