Schemata of a multi-proxy approach to interpreting hypoxia categories, including severe hypoxia ([O₂]<0.5 ml L^-1), intermediate hypoxia ([O₂]>0.5–1.5 ml L^-1) and mild hypoxia to oxic conditions ([O₂]>1.5 ml L^-1).

<p>These hypoxia categories are detailed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115246#pone.0115246.t001" target="_blank">Table 1</a>, and follow <i>Hofmann et al.</i>, [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115246#pone.0115246.ref024" target="_blank">24</a>]. Hypoxia proxies include [Re], [Mn], [U], [Cd], [Mo], δ¹⁵N, foraminiferan communities, and sedimentary laminations. Units for each proxy reflect the cited literature, which constrains the proxy to a specific oxygenation category.</p

Subarctic Pacific (SP) deglacial core data synthesized into hypoxia categories.

<p>Changing deglacial core depths reflect global eustatic sea level change. The encircled number adjacent to each core label corresponds to the number of available oxygenation proxies, which are enumerate in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115246#pone.0115246.t003" target="_blank">Table 3</a>. Vertical grey bars correlate to temporal intervals in OMZ geospatial reconstructions for this region.</p

Deglacial changes in Antarctic temperature (Vostok ice core record, purple line) [146, 147], Greenland temperature (GISP2 ice core record, blue line) [106, 107], sea level (black line) [5, 6] and atmospheric pCO₂ (red line) [3].

<p>Glacial Termination IA (14.7 ka) is an event of rapid warming in the Northern Hemisphere, which initiates the warm interval of the Bølling-Allerød (B/A) from 14.7–12.9 ka. The Younger Dryas (YD), a reversal towards cool conditions from 12.9–11.7 ka, follows the B/A. The YD ends with glacial Termination IB (11.7 ka), a subsequent rapid warming event. Deglacial warming in the Southern Hemisphere begins at 18 ka.</p

Equatorial Pacific and Humboldt Current bathymetric seafloor masks and surface area (km²) histograms of deglacial hypoxia impingement for (a) 18 ka, (b) 13 ka, (c) 10 ka, and (d) 4 ka.

<p>Seafloor is selected between 0–3,300 mbsl and latitudinally constrained between 10° 30′ N-32° S. Analyses were limited to the continental margin within a 400 nautical mile buffer offshore of the continental coastline and the Galapagos Islands. The changing gray shoreline through the panels depicts the paleo-shoreline. At 18 ka, severe hypoxia was limited from 937–1,037 mbsl. At 18 ka, intermediate hypoxia was found in deep water (2,082–3,088 mbsl). At 13 ka, severe hypoxia was found between 108–331 mbsl, and intermediate hypoxia was deeper (332–3,130 mbsl). At 10 ka, severe hypoxia was again found in shallow waters (315–415 mbsl) and intermediate hypoxia was deeper (415–3,164 mbsl). At 4 ka, intermediate hypoxia retracted to between 1,313–1,413 mbsl.</p

Surface area calculations of deglacial oxygenation changes for four Eastern Pacific continental margins: Subarctic Pacific (SP), California Current (CC), Mexico Margin (MM), and the Humboldt Current and Equatorial Pacific (HC).

<p>Surface area calculations of deglacial oxygenation changes for four Eastern Pacific continental margins: Subarctic Pacific (SP), California Current (CC), Mexico Margin (MM), and the Humboldt Current and Equatorial Pacific (HC).</p

Hypoxia categories and associated oxygen concentrations, partial pressures and saturations for each category.

<p>Hypoxia categories and associated oxygen concentrations, partial pressures and saturations for each category.</p

Subarctic Pacific bathymetric seafloor masks and surface area (km²) histograms of deglacial hypoxia impingement for (a) 14 ka, (b) 10 ka, and (c) 4 ka.

<p>The Bering Sea and Sea of Okhotsk are not included in the analysis, due to their unique, regional-scale oceanography. Seafloor is selected between 0–3,200 mbsl, with a southern latitude limit at 38° 30′ N in the Western Pacific and 49° 30′ N in the Eastern Pacific with a northern limit along the Aleutian Arc. Analyses were limited to the continental margin within a 400 nautical mile buffer offshore of the continental coastline and the Aleutian Arc. The changing gray shoreline through the panels depicts the paleo-shoreline. At 14 ka, severe hypoxia ranged from 596–2,894 mbsl. At 10 ka, the water column was oxygenated, and at 4 ka severe hypoxia was found between 132–232 mbsl.</p

California Current bathymetric seafloor masks and surface area (km²) histograms of deglacial hypoxia impingement for (a) 18 ka, (b) 14 ka, (c) 12 ka, (d) 10 ka, and (e) 4 ka.

<p>Seafloor is selected between 0–2,400 mbsl and latitudinally constrained between 31° 40′-49° 30′ N. Analyses were limited to the continental margin within a 400 nautical mile buffer offshore of the continental coastline. The changing gray shoreline through the panels depicts the paleo-shoreline. The seafloor was oxic at 18 ka. At 14 ka the seafloor was severely hypoxic (395–869 mbsl), and bracketed by intermediate hypoxia above (332–395 mbsl) and below (869–1,564 mbsl). The seafloor returned to an oxic state at 12 ka. At 10 ka severe hypoxia (436–525 mbsl) was bracketed by intermediate hypoxia (373–436 mbsl, 525–1,605 mbsl). At 4 ka severe hypoxia (525–625 mbsl) was bracketed by intermediate hypoxia (417–525 mbsl,625–954 mbsl).</p

Seafloor hypoxia proxies for paleoceanographic reconstructions, partitioned by the thresholds and capacity each proxy has to record fine-scale changes in seafloor hypoxia, as well as organic flux to the seafloor [24].

<p>Seafloor hypoxia proxies for paleoceanographic reconstructions, partitioned by the thresholds and capacity each proxy has to record fine-scale changes in seafloor hypoxia, as well as organic flux to the seafloor [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115246#pone.0115246.ref024" target="_blank">24</a>].</p

Global Oxygen Minimum Zones, including (a) Upper depth (in meters) of intermediate water hypoxia ([O₂]<1.4 ml L^-1) and (b) thickness (in meters) of intermediate water hypoxia ([O₂]<1.4 ml L^-1).

<p>The geospatial distributions of severely hypoxic [O₂] minimums (of [O₂] = 0.5 ml L^-1 and [O₂] = 0.2 ml L^-1) are depicted on both panels as white lines. For the upper panel, regional blocks are defined by black lines to highlight where paleoxygenation reconstructions were completed. Data from World Ocean Atlas [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115246#pone.0115246.ref192" target="_blank">192</a>].</p