Centennial OMZ changes in the NW Mexican Margin from geochemical and foraminiferal sedimentary records

Ontiveros-Cuadras, Jorge Feliciano; Thunell, Robert C.; Ruiz-Fernández, Ana Carolina; Benítez-Nelson, Claudia R.; Tappa, Eric; Sanchez-Cabeza, Joan-Albert

doi:10.1016/j.csr.2019.02.009

Cited by 7 publications

(8 citation statements)

References 77 publications

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“…Correlation between U and Mo in sediments collected under (A) oxic or moderately hypoxic waters and (B) severely hypoxic or anoxic waters from different basins of the Eastern Tropical North Pacific (Data from: this study;Ivanochko and Pedersen, 2004;McManus et al, 2006;Choumiline et al, 2017; EarthChem database with n = 183).the mid-1990s, followed by a slight possible OMZ intensification over the last decade as shown by some of our proxy V and U auth data from Alfonso and La Paz basins in accordance with the findings ofTems et al (2016),Ontiveros-Cuadras et al (2019) and a high-resolution U record of the last century byChoumiline et al (2010) andChoumiline (2011).…”

supporting

confidence: 86%

“…As indicated by Tems et al (2016) and confirmed by our findings, despite a decline in measured O 2 values in the Eastern Pacific over the last few decades (Bograd et al, 2003(Bograd et al, , 2008Levin, 2018), sedimentary records of the ETNP do not indicate increasing anoxia. Our geochemical proxy data from Alfonso from this study, Pescadero (Tems et al, 2016), and Mazatlan Margin (Ontiveros-Cuadras et al, 2019) also confirm that despite the recent warming trend and related anthropogenically triggered ocean-scale O 2 decline (Bograd et al, 2003(Bograd et al, , 2008Breitburg et al, 2018;Levin, 2018), the sedimentary records of benthic foraminifera, δ 15 N, Cd, Mo, U auth , and V do not suggest a significant increase in anoxia after the mid-1800s (Figures 4, 8).…”

Section: Drivers Of Redox In the Eastern Pacific And Apparent Contradsupporting

confidence: 70%

“…Due to their locations near the open Pacific Ocean, the southern basins are a sensitive recorder of regional variation in the GC and the larger-scale climate circulation of the ETNP, capturing changes in productivity and redox conditions useful for tracking fluctuations of the OMZ (Dean et al, 2004;Barron and Bukry, 2007;Dean, 2007;Pérez-Cruz, 2013;Deutsch et al, 2014;Tems et al, 2015Tems et al, , 2016Ontiveros-Cuadras et al, 2019).…”

Section: Depositional Settingmentioning

confidence: 99%

“…It is important to note that some of the decreasing patterns could be biased by improvements in O 2 measurement technologies that have decreased minimum detection thresholds. Despite this caveat, high-resolution reconstructions of changes in dissolved oxygen in the ETNP OMZ over the past century yield contrasting observations, with warming and increasing extent of anoxia (<0.1 mL/L O 2 ) not always correlated (Choumiline, 2011;Deutsch et al, 2014;Tems et al, 2016;Fu et al, 2018;Ontiveros-Cuadras et al, 2019). Ongoing discussions about the causes of OMZ intensification over the past decades typically invoke decreased O 2 solubility due to warming of the upper ocean, increased stratification slowing ventilation (Oschlies et al, 2008;Shaffer et al, 2009;Moffitt et al, 2015;Praetorius et al, 2015;Fu et al, 2018), and the strong effect of enhanced marine productivity on the formation of settling organic matter that undergoes decay and consumes more O 2 during remineralization (Wright et al, 2012;Levin, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Scenarios of Deoxygenation of the Eastern Tropical North Pacific During the Past Millennium as a Window Into the Future of Oxygen Minimum Zones

et al. 2019

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Diverse studies predict global expansion of Oxygen Minimum Zones (OMZs) as a consequence of anthropogenic global warming. While the observed dissolved oxygen concentrations in many coastal regions are slowly decreasing, sediment core paleorecords often show contradictory trends. This is the case for numerous high-resolution reconstructions of oxygenation in the Eastern Tropical North Pacific (ETNP). While major shifts in redox conditions of the ETNP are dominated by glacial-interglacial cycling, important fluctuations also occur in response to minor climatic and oceanographic perturbations. It is important to understand these scenarios of past redox variation, as they are the closest analog for near future climate and oceanographic change. We present recently collected sediment core proxy records from the Gulf of California in which we reproduce the variability of productivity and oxygenation of the ETNP OMZ during the past millennium. We emphasize paleoproductivity (C org , Ni, Ba excess ) and paleoredox indicators (Mo, Cd, V, U auth ) in sediment cores collected in Alfonso and La Paz basins and compare these OMZ records with other archives of the Eastern Pacific. Our findings indicate that the OMZ expanded in response to increased upwelling and productivity during cold intervals of the early 1400s, early 1500s, late 1600s, and early 1800s AD (evidenced by higher Ni, V, Cd, Mo, and U auth ). The most hypoxic times corresponded to the beginning of the Little Ice Age (expressed in elevated Mo). Significant OMZ contractions occurred around late 1300s, early 1700s, and late 1900s AD after reoxygenation events that were instigated by low productivity (lower Ni, V, Cd, Mo, and U auth ). The mechanisms that control decadal-to-centennial oxygen variability in the ETNP remain unidentified but are likely influenced by solar forcing not only driving migrations of the Intertropical Convergence Zone (ITCZ) but more importantly changes in the intensity of the Pacific Walker Circulation (PWC). During the Little Ice Age solar irradiance was at its lowest for the past millennium, which strengthened the PWC. This pattern contributed to more frequent La Niña-like conditions, which enhanced upwelling of nutrient-rich waters in the west coast of North America, driving productivity and reducing bottom oxygen levels, as seen in our ETNP records.

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supporting

confidence: 86%

Section: Drivers Of Redox In the Eastern Pacific And Apparent Contradsupporting

confidence: 70%

Section: Depositional Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Scenarios of Deoxygenation of the Eastern Tropical North Pacific During the Past Millennium as a Window Into the Future of Oxygen Minimum Zones

et al. 2019

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“…Likewise, the presence (although scarcer than gypsum) of pyrite in framboidal form (packed spherical aggregates of pyrite crystals, Wilkin et al, 1996) is also a sign of high levels of anoxia and a chemocline positioned at the water-sediment surface favoring the dissolution of calcite (Tribovillard et al, 2006), which adds another probable cause for the disappearance of benthic and planktonic foraminifera at the above-mentioned levels. Intense dissolution associated with near anoxic conditions is supported by Ontiveros-Cuadras et al (2019), who found high molybdenum and uranium (redox-sensitive trace elements) where foraminifera were absent. Upwelling and resulting high production rates contribute to fluctuations of carbonate saturation in oxygen-poor habitats that in turn produce changes in foraminiferal calcite (Gibson et al, 2016).…”

Section: Discussionmentioning

confidence: 89%

Paleoceanographic evolution of the Gulf of Tehuantepec (Mexican Pacific) during the last ~6 millennia

García-Gallardo

Almaraz-Ruiz

2020

The Holocene

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Oceanographic dynamics in the Gulf of Tehuantepec (GT) are the direct consequence of climate variability, mainly influenced by the strong wind regime locally called “Tehuanos” and the interactions between the Intertropical Convergence Zone (ITCZ) and El Niño Southern Oscillation (ENSO). The area is characterized by intense upwelling driven by the Tehuanos within one of the largest Oxygen Minimum Zones (OMZ) in the world. Upwelling carries nutrient-rich subsurface waters to the surface and provides marine resources to the coasts conforming one of the main economic sectors in the region. In this study, sediment core MD02-2521 is used to perform the first high-resolution paleoceanographic reconstruction of the last 6 millennia in the GT. The main focus is put on the analysis of the benthic foraminifera (BF) assemblages inhabiting within the OMZ, which appear to respond to bottom oxygenation and climate variations of the last ~6000 years. The microfossil assemblages throughout the sediment core revealed, first, intervals where the lack of foraminifera provide evidence of episodes of strong deoxygenation that triggered the dissolution of calcareous foraminiferal tests, second, a long-term decline of bottom-water oxygenation in the last ~2500 years likely responding to the southward migration of the ITCZ. Last, variations in response to the transitions between cold and warm periods occurred during the last 2–2.5 millennia and cyclicities of 1470 years resembling Bond Cycles suggest a climatic connection between the Pacific and Atlantic Oceans during the late-Holocene.

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Rapid expansion of fixed nitrogen deficit in the eastern Pacific Ocean revealed by 50 year time series

Evans

Tichota

Ruef

et al. 2022

Preprint

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Climate change is expected to increase the strength of ocean Oxygen Deficient Zones (ODZs), but we lack detailed understanding of the temporal or spatial variability of these ODZs. A fifty-year time series in the Eastern Tropical North Pacific (ETNP) ODZ revealed that it strengthened by 30% from 1994 to 2019. We subdivided the ODZ into a core and a deep layer based on potential density and revealed that different processes control the magnitude of fixed nitrogen loss in these two regions.We postulate that the depth of the upper ETNP ODZ water mass, the 13 ºC water, influences the organic carbon supply to the core ODZ and therefore its strength. We correlated the fixed nitrogen loss in the core ODZ with a nearby sedimentary nitrogen isotope record and found that this recent, rapid increase has only occurred a few times over the last 1200 years. Using this correlation, we derived the first confidence interval for the strength of the core ETNP ODZ, 9.2-12.5 μmol kg-1 of fixed nitrogen loss. While the current increase is comparable to only two previous events, it is still within this confidence interval. Nevertheless, climate driven intensification could lead to unprecedented changes within the next decade. The deep ODZ also strengthened from 2016-2019 by approximately 30%, even more rapidly than the core ODZ. This dramatic increase was not observed over the rest of the 50-year time series.

show abstract

Centennial OMZ changes in the NW Mexican Margin from geochemical and foraminiferal sedimentary records

Cited by 7 publications

References 77 publications

Scenarios of Deoxygenation of the Eastern Tropical North Pacific During the Past Millennium as a Window Into the Future of Oxygen Minimum Zones

Scenarios of Deoxygenation of the Eastern Tropical North Pacific During the Past Millennium as a Window Into the Future of Oxygen Minimum Zones

Paleoceanographic evolution of the Gulf of Tehuantepec (Mexican Pacific) during the last ~6 millennia

Rapid expansion of fixed nitrogen deficit in the eastern Pacific Ocean revealed by 50 year time series

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