Deglacial 14C reservoir ages of surface waters at the northern boundary of Peruvian coastal upwelling

2020 ◽  
Author(s):  
Nicolaas Glock ◽  
Michael Sarnthein ◽  
Kristin Doering ◽  
Gesine Mollenhauer ◽  
Renato Salvatteci
Keyword(s):  
Coastal Upwelling ◽  
Trade Wind ◽  
Small Scale ◽  
Age Difference ◽  
Northern Boundary ◽  
Neogloboquadrina Dutertrei ◽  
Minimum Zone ◽  
Age Model ◽  
The Difference ◽  
Oxygen Minimum

<p>To constrain the accurate age of a marine sediment record, the radiocarbon (<sup>14</sup>C) ages need to be corrected for short-term and small-scale changes in planktic <sup>14</sup>C reservoir ages (R<sub>plank</sub>). Nevertheless, accurate records of past changes in R<sub>plank</sub> are scarce. Here we present a high-resolution record of deglacial <sup>14</sup>C ages measured on <em>Globigerina bulloides</em> in sediment core M77/2-59-1 from the northern boundary (~4°S, 997 m) of the Peruvian upwelling zone. The fine structure of jumps and plateau boundaries in the <sup>14</sup>C record were tuned to synchronous, thus global structures in the atmospheric <sup>14</sup>C record of Lake Suigetsu (Bronk Ramsey et al., 2012) and used as tie points for an age model with semi-millennial resolution, moreover to reconstruct deglacial changes in R<sub>plank </sub>from 17 to 11 cal. ka. In our record, R<sub>plank</sub> drops from 1250 <sup>14</sup>C yr prior to 14 cal. ka to ~600 – 450 <sup>14</sup>C yr until the plateau named Top of Younger Dryas. The drop suggests a major decrease in coastal upwelling, possibly the result of a southward (poleward) expansion of the Intertropical Convergence Zone and related shift in the southeastern trade wind belt during the Bølling-Allerød. Subsequent to 14 cal. ka our R<sub>plank </sub>values are roughly similar to values obtained for thermocline waters near the equator from the age difference between <sup>14</sup>C ages of wood chunks and <sup>14</sup>C of <em>G. ruber</em> (Zhao & Keigwin, 2018). Prior to 14 cal. ka our R<sub>plank </sub>are ~800 <sup>14</sup>C yr higher, which corroborates the presumed latitudinal shift of coastal upwelling. Our <sup>14</sup>C ages measured on G. bulloides differ in part from paired <sup>14</sup>C ages of <em>Neogloboquadrina dutertrei</em>, indicating their habitat in different water masses prior to 14 cal. ka, in support of the upwelling affinity of <em>G. bulloides</em>. In addition, we used our R<sub>plank</sub> values to accurately derive past ventilation ages of intermediate waters near 1000 m depth based on the difference of paired benthic and planktic <sup>14</sup>C ages, which is important to constrain centennial to millennial scale changes in circulation influencing the extent of the Peruvian oxygen minimum zone.</p><p>References:</p><p>Bronk Ramsey, C., et al., Science, 338, 370–374, 2012.</p><p>Zhao & Keigwin, Nature communications, 9, 3077, 2018.</p>

scholarly journals Differences between coastal and open ocean distributions of N<sub>2</sub>O in the oxygen minimum zone off Peru

2015 ◽  
Vol 12 (13) ◽  
pp. 10167-10193 ◽  
Author(s):  
A. Kock ◽  
D. L. Arévalo-Martínez ◽  
C. R. Löscher ◽  
H. W. Bange
Keyword(s):  
Linear Relationship ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Open Ocean ◽  
Oxygen Utilization ◽  
Double Peak Structure ◽  
Peak Structure ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. Depth profiles of nitrous oxide (N2O) were measured during six cruises to the upwelling area and oxygen minimum zone (OMZ) off Peru in 2009 and 2012/13, covering both the coastal shelf region and the adjacent open ocean. N2O profiles displayed a strong sensitivity towards oxygen concentrations. Open ocean profiles showed a transition from a broad maximum to a double-peak structure towards the centre of the OMZ where the oxygen minimum was more pronounced. Maximum N2O concentrations in the open ocean were about 80 nM. A linear relationship between ΔN2O and apparent oxygen utilization (AOU) could be found for all measurements within the upper oxycline, with a slope similar to studies in other oceanic regions. N2O profiles close to the shelf revealed a much higher variability, with N2O concentrations in the upper oxycline reaching up to several hundred nanomoles per liter at selected stations. Due to the extremely sharp oxygen gradients at the shelf, these maxima occurred in very shallow water depths of less than 50 m. In this area, a linear relationship between ΔN2O and AOU could not be observed. N2O concentrations above 100 nM were observed at oxygen concentrations ranging from close to saturation to suboxic conditions. Our results indicate that the coastal upwelling off Peru at the shelf causes conditions that lead to extreme N2O accumulation.

Contribution of oxygen minimum zone waters to the coastal upwelling off Mauritania

2009 ◽  
Vol 83 (1-4) ◽  
pp. 143-150 ◽  
Author(s):  
Mirjam S. Glessmer ◽  
Carsten Eden ◽  
Andreas Oschlies
Keyword(s):  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Benthic Foraminifera from Middle to Late Pleistocene, coastal upwelling sediments of ODP Hole 686B, Pacific Ocean, off Peru

1991 ◽  
Vol 9 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Kathryn A. Malmgren ◽  
Brian M. Funnell
Keyword(s):  
Late Pleistocene ◽  
Surface Waters ◽  
Benthic Foraminifera ◽  
Bottom Water ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Water Oxygen ◽  
Minimum Zone ◽  
Water Depths ◽  
Oxygen Minimum

Abstract. Benthic Foraminifera from middle to late Pleistocene, (c. 600ka to 0ka), sediments of ODP Hole 686B, off Peru, show highest abundances and diversities during periods of cooler surface waters, (inferred from the Uk37 index), and enhanced upwelling, (inferred from the peridinacean/gonyaulacacean dinoflagellate cyst ratio). During the latest Pleistocene, (c. 160ka to 0ka), these periods are characterised by higher organic carbon contents in the bottom sediments, and occur during the odd-numbered, interglacial_18O stages. The benthic Foraminifera indicate deposition in 120 to 250 metres water depth for the earlier part of the record, (c. 600ka to c. 200ka), within the oxygen-minimum zone, with bottom water oxygen contents of <0.5 to 0.2 ml/l, (inferred from the dominance of Bolivinellina humilis). Deposition in water depths approaching those of the present day, (c. 450 metres), is indicated from c. 160ka onwards, with better oxygenated bottom water conditions, probably corresponding to the lower part of the oxygen-minimum zone.

Oxygen-minimum zone edge effects: Evidence from the central California coastal upwelling system

Geology ◽  
1985 ◽  
Vol 13 (7) ◽  
pp. 491 ◽  
Author(s):  
Henry T. Mullins ◽  
Joel B. Thompson ◽  
Kristin McDougall ◽  
Thomas L. Vercoutere
Keyword(s):  
Edge Effects ◽  
Coastal Upwelling ◽  
Oxygen Minimum Zone ◽  
Central California ◽  
Upwelling System ◽  
Minimum Zone ◽  
Zone Edge ◽  
Oxygen Minimum

scholarly journals Temporal and vertical variability of bacterioplankton composition in Chipana bay (21º20’S) in a coastal upwelling system of northern Chile: A fluorescence in situ hybridization approach

2020 ◽  
Vol 55 (1) ◽  
pp. 47
Author(s):  
Cristy Medina-Armijo ◽  
Rubén Moraga-Mamani ◽  
Edgardo Santander-Pulgar
Keyword(s):  
In Situ Hybridization ◽  
Coastal Upwelling ◽  
Surface Layers ◽  
Gamma Proteobacteria ◽  
Minimum Zone ◽  
Taxonomic Groups ◽  
Alpha Proteobacteria ◽  
The Vertical Distribution ◽  
Oxygen Minimum

The bacterioplankton in the upwelling systems associated with oceanographic condition of the oxygen minimum zone (OMZ) of the Eastern tropical South Pacific was studied through visualization and enumeration with fluorescent in situ hybridization (FISH). Six different taxonomic groups were studied (Alpha, Beta, Gamma-proteobacteria, Cytophaga-flavobacterium and the domains Archaea and Bacteria). The analysis showed a greater predominance of the Bacteria domain (20 to 68% of hybridized cells) over Archaea (2 to 18% of hybridized cells). The specific groups showed that Cytophaga-flavobacterium, Alpha-proteobacteria and Gamma-proteobacteria are more abundant in the surface layer. Gamma-proteobacteria is also most abundant in the deep oxycline and, Beta-proteobacteria is the group with the lowest registered abundances. Changes in the vertical distribution of the bacterial community in the water column between OMZ and on oxycline were observed through NMDS. This change is a product of a shift in the abundances of the specific groups Cytophaga-flavobacterium and Gamma-proteobacteria in the surface layers, due to low concentration of chlorophyll-a caused by periods of relaxation in the upwelling. 

scholarly journals Extreme N<sub>2</sub>O accumulation in the coastal oxygen minimum zone off Peru

2016 ◽  
Vol 13 (3) ◽  
pp. 827-840 ◽  
Author(s):  
A. Kock ◽  
D. L. Arévalo-Martínez ◽  
C. R. Löscher ◽  
H. W. Bange
Keyword(s):  
Linear Relationship ◽  
Coastal Upwelling ◽  
Nitrogen Loss ◽  
Full Range ◽  
Oxygen Minimum Zone ◽  
Open Ocean ◽  
N2o Production ◽  
Minimum Zone ◽  
Oxygen Minimum ◽  
Oxygen Concentrations

Abstract. Depth profiles of nitrous oxide (N2O) were measured during six cruises to the upwelling area and oxygen minimum zone (OMZ) off Peru in 2009 and 2012/2013, covering both the coastal shelf region and the adjacent open ocean. N2O profiles displayed a strong sensitivity towards oxygen concentrations. Open ocean profiles with distances to the shelf break larger than the first baroclinic Rossby radius of deformation showed a transition from a broad maximum close to the Equator to a double-peak structure south of 5° S where the oxygen minimum was more pronounced. Maximum N2O concentrations in the open ocean were about 80 nM. A linear relationship between ΔN2O and apparent oxygen utilization (AOU) could be found for measurements within the upper oxycline, with a slope similar to studies in other oceanic regions. In contrast, N2O profiles close to the shelf revealed a much higher variability, and N2O concentrations higher than 100 nM were often observed. The highest N2O concentration measured at the shelf was  ∼  850 nM. Due to the extremely sharp oxygen gradients at the shelf, N2O maxima occurred in very shallow water depths of less than 50 m. In the coastal area, a linear relationship between ΔN2O and AOU could not be observed as extremely high ΔN2O values were scattered over the full range of oxygen concentrations. The data points that showed the strongest deviation from a linear ΔN2O ∕ AOU relationship also showed signals of intense nitrogen loss. These results indicate that the coastal upwelling at the Peruvian coast and the subsequent strong remineralization in the water column causes conditions that lead to extreme N2O accumulation, most likely due to the interplay of intense mixing and high rates of remineralization which lead to a rapid switching of the OMZ waters between anoxic and oxic conditions. This, in turn, could trigger incomplete denitrification or pulses of increased nitrification with extreme N2O production.

Future trends in oxygen minimum zone volume are sensitive to model representation of iron

2020 ◽  
Author(s):  
Wanxuan Yao ◽  
Karin Kvale ◽  
Angela Landolfi ◽  
Wolfgang Koeve ◽  
Eric Achterberg ◽  
...  
Keyword(s):  
Oxygen Minimum Zone ◽  
Low Latitude ◽  
Surface Ocean ◽  
Minimum Zone ◽  
The Difference ◽  
Business As Usual ◽  
The Impact ◽  
Production Response ◽  
Oxygen Minimum

&lt;p&gt;Increasing the complexity&amp;#160;of the representation of iron in an earth system model can lead to significant differences in surface ocean nutrient pathways in a pre-industrial climate. These differences persist even after automated calibration forces the models to achieve similar fit to the same observational data. We explore the impact of these nutrient pathway differences in the context of climate change by forcing the models (one without iron, one with a seasonally-cyclic iron mask, and one with a fully dynamic iron module) with the RCP8.5 business-as-usual atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration scenario from years 1800 until 2100. We find that while the global oxygen inventory drops across all models over this period, different trends in the oxygen minimum zone (OMZ) volume arise. Models with iron represented simulate decreases between 60 and 80 percent in OMZ volume, while the model without iron simulates an OMZ volume increase of 10 percent. The difference is attributed to the role of iron limitation in regulating the low latitude primary production response to warming and stratification. We further quantify the corresponding denitrification trends and impact on ocean nitrate inventory.&amp;#160;This study illustrates that model structural uncertainty further challenges predictions under a changing climate, and highlights the strong role of iron in regulating nutrient cycling and ocean deoxygenation.&lt;/p&gt;

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