Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 21
Biogeosciences, 15, 6747-6759, 2018
https://doi.org/10.5194/bg-15-6747-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Biogeosciences, 15, 6747-6759, 2018
https://doi.org/10.5194/bg-15-6747-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Nov 2018

Research article | 13 Nov 2018

The effect of the 2013–2016 high temperature anomaly in the subarctic Northeast Pacific (the “Blob”) on net community production

Bo Yang1,a, Steven R. Emerson1, and M. Angelica Peña2 Bo Yang et al.
  • 1School of Oceanography, University of Washington, Seattle, WA 98195, USA
  • 2Institute of Ocean Sciences, Fisheries and Oceans Canada, P.O. Box 6000, Sidney, BC, V8L 4B2, Canada
  • apresent address: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA

Abstract. A large anomalously warm water patch (the Blob) appeared in the NE Pacific Ocean in the winter of 2013–2014 and persisted through 2016 causing strong positive upper ocean temperature anomalies at Ocean Station Papa (OSP, 50°N, 145°W). The effect of the temperature anomalies on annual net community production (ANCP) was determined by upper ocean chemical mass balances of O2 and dissolved inorganic carbon (DIC) using data from a profiling float and a surface mooring. Year-round oxygen mass balance in the upper ocean (0 to 91–111m) indicates that ANCP decreased after the first year when warmer water invaded this area and then returned to the pre-Blob value (2.4, 0.8, 2.1, and 1.6molCm−2yr−1 from 2012 to 2016, with a mean value of 1.7±0.7molCm−2yr−1). ANCP determined from the DIC mass balance has a mean value that is similar within the errors as that from the O2 mass balance but without a significant trend (2.0, 2.1, 2.6, and 3.0molCm−2yr−1 with a mean value of 2.4±0.6molCm−2yr−1). This is likely due to differences in the air–sea gas exchange, which is a major term for both mass balances. Oxygen has a residence time with respect to gas exchange of about 1 month while the CO2 gas exchange response time is more like a year. Therefore the biologically induced oxygen saturation anomaly responds fast enough to record annual changes, whereas that for CO2 does not. Phytoplankton pigment analysis from the upper ocean shows lower chlorophyll a concentrations and changes in plankton community composition (greater relative abundance of picoplankton) in the year after the warm water patch entered the area than in previous and subsequent years. Our analysis of multiple physical and biological processes that may have caused the ANCP decrease after warm water entered the area suggests that it was most likely due to the temperature-induced changes in biological processes.

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A large anomalously warm water patch appeared in the NE Pacific in winter 2013–14 and persisted through 2016. Its effect on biological carbon export was determined using O2 and dissolved inorganic carbon data from a profiling float and a surface mooring. Results show the carbon export decreased after the first year when warmer water invaded and then returned to the previous value, with a similar trend in phytoplankton abundance and corresponding changes in phytoplankton community composition.
A large anomalously warm water patch appeared in the NE Pacific in winter 2013–14 and persisted...
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