Nutrient enrichment of the subarctic Pacific Ocean pycnocline

• Published in: Geophysical research letters Vol. 40; no. 10; pp. 2200 - 2205
• Main Authors: Whitney, Frank A., Bograd, Steven J., Ono, Tsuneo
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 28.05.2013; John Wiley & Sons, Inc
• Subjects: Ablation; Budgeting; Circulation; Climate; Climate models; Compressing; Compression; Density stratification; Dissolution; Dissolving; Ecosystem models; Enrichment; Environment models; Geophysics; Ice; Marine; Mineral nutrients; Nitrates; nutrient cycling; Nutrient enrichment; Nutrient loss; Nutrients; Oceans; Oxygen; oxygen transport; Particulates; Pycnocline; Sinking; Stratification; subarctic Pacific; Surface boundary layer; Surface layer; Surface layers; Temperature (air-sea); Thermohaline circulation; time-series; Trends; Upper ocean
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/grl.50439

At the end of the global thermohaline circulation, the subarctic Pacific is the richest nutrient repository in the world oceans. Trends towards lower oxygen and higher nutrients in waters below the surface layer (the pycnocline) have been observed in recent decades. We assess these trends using data from four programs and suggest the enrichment of pycnocline nitrate (200 Gmol y−1) is essential in keeping supply to the surface ocean constant, despite increasing upper ocean stratification. A nitrate budget helps identify possible vertical processes that could account for nutrient redistribution. We hypothesize that warming and oxygen loss in the deeper pycnocline, arising from ice loss in the Okhotsk Sea, have initiated a largely vertical redistribution of nutrients due to compression of vertical migrator habitat and/or changes in dissolution of sinking particulates. Coupled climate‐ecosystem models will need to incorporate these processes to more fully understand projected changes in the subarctic Pacific. Key Points•nutrients are accumulating in the pycnocline of the subarctic Pacific•pycnocline nutrients maintain winter supply to the surface layer•shallower remineralization due to hypoxia or reduced sinking rates