Intermediate water circulation drives distribution of Pliocene Oxygen Minimum Zones

Davis, Catherine V.; Sibert, Elizabeth C; Jacobs, Peter; Burls, Natalie J.; Hull, Pincelli M.

doi:10.1038/s41467-022-35083-x

Cited by 6 publications

(7 citation statements)

References 85 publications

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“…The regions of modeled maximum mixed layer depths and NPDW formation are predominantly found in the western subarctic North Pacific and Bering Sea (i.e., near ODP 882) (Figure 6), suggesting that these locations would still be relevant areas of NPDW formation as PMOC weakened, while any NPDW formation in the eastern subarctic North Pacific (i.e., near ODP 887 and IODP U1417) would likely only occur under stronger PMOC conditions (Burls et al., 2017; Menviel et al., 2012; Thomas et al., 2021). Lower TOC fluxes in the eastern subarctic North Pacific prior to ∼3.6 Ma point to a more well‐mixed and oxygenated water column (Sánchez Montes et al., 2022), which is also observed in model simulations (Figure 6a) (Davis et al., 2023; Menviel et al., 2012), supporting early Pliocene NPDW formation at the site. The opposite is true for the western subarctic North Pacific if CaCO 3 fluxes primarily reflect deep water corrosivity, as ODP 882 CaCO 3 fluxes are the highest after ∼3.6–3.8 Ma (Burls et al., 2017).…”

Section: Discussionsupporting

confidence: 61%

“… Modeled Pliocene North Pacific oxygen concentrations and water mass transport. (a) Early Pliocene minus Preindustrial dissolved oxygen anomalies (CESM v. 1.2.2, configuration T31 gx3v7) (Davis et al., 2023). The model output is taken at 168°W, the longitude of ODP 885/886.…”

Section: Discussionmentioning

confidence: 99%

“…(2022), and Davis et al. (2023)), (b) whether preservation is the only driver of variability in the flux across the entire Pliocene, and (c) if the flux is purely recording bottom water conditions, how much of the subarctic North Pacific basin is integrated into the overall signal. We elaborate on these potential complications in Text S4 in Supporting Information .…”

Section: Discussionmentioning

confidence: 99%

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Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World

Abell,

Winckler

2023

AGU Advances

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Unlike in the high‐latitude North Atlantic, no deep water is formed in the modern subarctic North Pacific. It has previously been suggested that during climate states different from today, this dichotomy did not endure, and the formation of North Pacific Deepwater (NPDW) occurred in the subarctic North Pacific, which supported an active Pacific meridional overturning circulation (PMOC). Here we provide new records of productivity and sedimentary redox conditions from the central subarctic North Pacific spanning the late Miocene to early Pleistocene. These reconstructions indicate greater‐than‐modern and temporally varying North Pacific export production across the interval of ∼2.7–6 Ma. Our time series, combined with previously published data sets and model output for Pliocene North Pacific Ocean dynamics, support the presence of an active PMOC during the Pliocene, and suggest that the characteristics of NPDW formation varied during this warmer interval of Earth's history. This finding of elevated export production at a time of deep water formation presents a conundrum when considering Quaternary North Pacific Ocean dynamics, where subarctic North Pacific productivity declines during intervals when enhanced overturning is posited to occur. We evaluate our data considering the caveats of both (i.e., Pliocene and Quaternary North Pacific circulation) hypotheses, as well as additional mechanisms unrelated to ocean circulation. Because the Pliocene is a possible analogue for near‐future climate, our results and analyses have important ramifications for our understanding of regional and global climate in the coming decades as the planet continues to warm.

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Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World

Abell,

Winckler

2023

AGU Advances

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“…Our knowledge about planktic foraminifera from O2 depleted habitats is scarce compared to our knowledge about benthic foraminifera. Nonetheless, at least two species Globorotaloides hexagonus and Hastigerina parapelagica are known to live in pelagic oxygen minimum zones (OMZs) (Davis et al, 2021) and therefore, G. hexagonus has proven to be a valuable paleo-indicator for the presence of pelagic OMZs during the Pliocene (Davis et al, 2023). In general, also benthic foraminifera from low O2 environments have been established as an invaluable archive for paleoceanography.…”

Section: Introductionmentioning

confidence: 99%

Reviews and syntheses: Foraminifera from anaerobic environments – Survival strategies, biogeochemistry, ecology and applications for paleoceanography

Glock

2023

Preprint

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Abstract. The oceans are losing oxygen (O2) and oxygen minimum zones are expanding, due to climate warming (lower O2 solubility) and artificial fertilization related to agriculture. This ongoing trend is challenging for most marine taxa that are not well adapted to O2 depletion. For other taxa this trend might be advantageous, because they can withstand low O2 concentrations or thrive under anaerobic or even anoxic conditions. Benthic foraminifera are a group of protists that might benefit from ongoing ocean deoxygenation, since several foraminifera species possess adaptations to O2 depletion that are unique amongst eukaryotes. This paper reviews the current state of knowledge about foraminifera from low O2 environments. The specific survival strategies of foraminifera to withstand O2 depletion include an anaerobic metabolism, heterotrophic denitrification, symbiosis with bacteria, kleptoplasty and dormancy. These adaptations, especially the ability to denitrify by some benthic foraminiferal species, have a strong impact on their preferred microhabitat in the sediments, which will be discussed in detail. In addition, due to their high abundances in O2 depleted environments and their metabolic adaptations, benthic foraminifera are key players in marine nutrient cycling, especially within the marine N and P cycles. Studies about the ecology of benthic foraminifera are scarce but there is evidence that foraminifers have the capacity of phagocytosis, even under anoxia, and some foraminiferal species, which can withstand low O2 conditions, even seem to prey on meiofauna. Finally, the fact that foraminifera can calcify even under anaerobic conditions makes them important archives for paleoceanographic applications. So this review will briefly summarize O2 proxies based on foraminiferal morphology, shell geochemistry and composition of foraminiferal assemblages.

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“…Here we use Laser Ablation ICP-MS for two reasons. The first is that G. hexagonus shells are both rare and light in many sediments (Davis et al, 2021, Davis et al, 2023, such that obtaining a sufficient sample for solution measurements may not always be possible. The second is anticipation of the potential need to use high-resolution intra-shell analyses to analytically distinguish between primary and altered calcite.…”

Section: Introductionmentioning

confidence: 99%

Trace element composition of modern planktic foraminifera from an oxygen minimum zone: Potential proxies for an enigmatic environment

et al. 2023

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Oxygen limited marine environments, such as oxygen minimum zones, are of profound importance for global nutrient cycling and vertical habitat availability. While it is understood that the extent and intensity of oxygen minimum zones are responsive to climate, the limited suite of viable proxies for low oxygen pelagic environments continues to pose a real barrier for paleoclimate interpretations. Here we investigate the proxy potential of an array of trace element (Mg, Mn, Zn, and Sr) to Ca ratios from the shells of Globorotaloides hexagonus, a planktic foraminifer endemic to tropical through temperate oxygen minimum zones. A species-specific relationship between Mg/Ca and temperature is proposed for quantitative reconstruction of oxygen minimum zone paleotemperatures. Both Mn/Ca and Zn/Ca ratios vary with oxygen concentration and could be useful for reconstructing G. hexagonus habitat where the primary signal can be d\istinguished from diagenetic overprinting. Finally, a robust correlation between Sr/Ca ratios and dissolved oxygen demonstrates a role for Sr as an indicator of oxygen minimum zone intensity, potentially via foraminiferal growth rate. The analysis of these relatively conventional trace element ratios in the shells of an oxygen minimum zone species has tremendous potential to facilitate multiproxy reconstructions from this enigmatic environment.

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Intermediate water circulation drives distribution of Pliocene Oxygen Minimum Zones

Cited by 6 publications

References 85 publications

Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World

Long‐Term Variability in Pliocene North Pacific Ocean Export Production and Its Implications for Ocean Circulation in a Warmer World

Reviews and syntheses: Foraminifera from anaerobic environments – Survival strategies, biogeochemistry, ecology and applications for paleoceanography

Trace element composition of modern planktic foraminifera from an oxygen minimum zone: Potential proxies for an enigmatic environment

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