1Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
2Pacific Marine Environmental Laboratory, NOAA, Seattle, WA 98115, USA
anow at: Carnegie Institution for Science, Stanford, CA 94305, USA
bnow at: University of Southern California, Los Angeles, CA 90089, USA
cnow at: Research Institution of Oceanography/School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, South Korea
dnow at: California State University Monterey Bay, Seaside, CA 93955, USA
enow at: Bigelow Laboratory for Ocean Sciences, East Boothbay, ME 04544, USA
Received: 15 Apr 2015 – Discussion started: 13 May 2015
Abstract. Assessing the impacts of anthropogenic ocean acidification requires knowledge of present-day and future environmental conditions. Here, we present a simple model for upwelling margins that projects anthropogenic acidification trajectories by combining high-temporal-resolution sensor data, hydrographic surveys for source water characterization, empirical relationships of the CO2 system, and the atmospheric CO2 record. This model characterizes CO2 variability on timescales ranging from hours (e.g., tidal) to months (e.g., seasonal), bridging a critical knowledge gap in ocean acidification research. The amount of anthropogenic carbon in a given water mass is dependent on the age; therefore a density–age relationship was derived for the study region and then combined with the 2013 Intergovernmental Panel on Climate Change CO2 emission scenarios to add density-dependent anthropogenic carbon to the sensor time series. The model was applied to time series from autonomous pH sensors deployed in the surf zone, kelp forest, submarine canyon edge, and shelf break in the upper 100 m of the Southern California Bight. All habitats were within 5 km of one another, and exhibited unique, habitat-specific CO2 variability signatures and acidification trajectories, demonstrating the importance of making projections in the context of habitat-specific CO2 signatures. In general, both the mean and range of pCO2 increase in the future, with the greatest increase in both magnitude and range occurring in the deeper habitats due to reduced buffering capacity. On the other hand, the saturation state of aragonite (ΩAr) decreased in both magnitude and range. This approach can be applied to the entire California Current System, and upwelling margins in general, where sensor and complementary hydrographic data are available.
Revised: 30 Aug 2015 – Accepted: 24 Sep 2015 – Published: 14 Oct 2015
Takeshita, Y., Frieder, C. A., Martz, T. R., Ballard, J. R., Feely, R. A., Kram, S., Nam, S., Navarro, M. O., Price, N. N., and Smith, J. E.: Including high-frequency variability in coastal ocean acidification projections, Biogeosciences, 12, 5853-5870, doi:10.5194/bg-12-5853-2015, 2015.