Reorganized Atmospheric Circulation During the Little Ice Age Leads to Rapid Southern California Deoxygenation
The magnitude of natural oceanic dissolved oxygen (DO) variability remains poorly understood due to the short duration of the observational record. Here we present a high‐resolution (4–9 years) reconstruction of the Southern California oxygen minimum zone (OMZ) through the Common Era using redox‐sen...
| Published in: | Geophysical Research Letters |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
Springer Berlin Heidelberg
2021
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| Subjects: | |
| Online Access: | https://hdl.handle.net/2027.42/169345 https://doi.org/10.1029/2021GL094469 |
| Summary: | The magnitude of natural oceanic dissolved oxygen (DO) variability remains poorly understood due to the short duration of the observational record. Here we present a high‐resolution (4–9 years) reconstruction of the Southern California oxygen minimum zone (OMZ) through the Common Era using redox‐sensitive metals. Rapid OMZ intensification on multidecadal timescales reveals greater DO variability than observed in instrumental records. An anomalous interval of intensified OMZ between 1600–1750 CE contradicts the expectation of better‐ventilated mid‐depth North Pacific during cool climates. Although the influence of low‐DO Equatorial Pacific Intermediate Water on the Southern California Margin was likely weaker during this interval, we attribute the observed rapid deoxygenation to reduced North Pacific Intermediate Water (NPIW) ventilation. NPIW ventilation thus appears very sensitive to atmospheric circulation reorganization (e.g., a weakened Siberian High and Aleutian Low). In addition to temperature‐induced gas solubility, atmospheric forcing under future anthropogenic influences could amplify OMZ variability.Plain Language SummaryOxygen content of the ocean is declining as seawater warms due to anthropogenic climate change impacting gas solubility. However, how much dissolved oxygen in seawater can decrease naturally is unknown, as we have only been measuring oxygen in ocean waters for ∼60 years. We reconstructed oxygen concentrations of bottom waters in Santa Barbara Basin (SBB), CA for the past 2,000 years using marine sediments on sub‐decadal time scales. We found that seawater oxygen varied more in the past than has been recently observed, and that seawater oxygen was surprisingly low during 1600–1750 CE—one of the coldest intervals during the last 1,000 years. At this time the atmospheric circulation over the Sea of Okhotsk suppressed sea ice formation, reducing the surface ocean mixing that supplies oxygen to the subsurface waters. This low‐oxygen subsurface water moved around the northeastern Pacific ... |
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