Decadal oscillations in the ocean's largest oxygen-deficient zone
N N Duprey1, A D Foreman1, J D Carriquiry2
1Max Planck Institute for Chemistry (Otto Hahn Institute), Mainz, Germany.
Science (New York, N.Y.)
|November 28, 2024
Summary
Ocean warming impacts oxygen-deficient zones (ODZs). Coral nitrogen isotopes reveal decadal shifts in Eastern Tropical North Pacific denitrification, linked to Pacific Decadal Variability, not just long-term global warming trends.
Area of Science:
- Marine chemistry
- Paleoceanography
- Climate science
Background:
- Ocean-warming effects on oxygen-deficient zones (ODZs) are unclear due to limited historical data.
- Understanding past ODZ changes is crucial for predicting future ocean deoxygenation.
Purpose of the Study:
- To reconstruct past denitrification in the Eastern Tropical North Pacific (ETNP) ODZ.
- To investigate the influence of decadal climate variability on ODZ dynamics.
Main Methods:
- Utilized coral skeleton-bound nitrogen isotopes (CS-δ15N) for monthly resolved records.
- Analyzed an 80-year time series of CS-δ15N from the ETNP.
Main Results:
- Observed significant decadal variations in ETNP denitrification and oxygen deficiency.
- Denitrification peaked during cool phases of the Pacific Decadal Variability.
- Stronger upwelling during these phases likely increased productivity and oxygen demand.
Conclusions:
- Decadal variability, particularly Pacific Decadal Variability, strongly influences ETNP ODZ dynamics.
- Previous long-term ODZ trend assessments may have been biased by decadal oscillations.
- Future ODZ evolution depends on the interplay between global warming and decadal climate patterns.
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