Event Title

Mechanisms that influence pH and aragonite saturation state in the Strait of Georgia

Presentation Abstract

A 1-D vertical biophysical coupled model is used to investigate the seasonal, interannual, and long-term variability of pH and aragonite saturation state in the southern Strait of Georgia. The model is initialized using casts from local sampling programs, and continuously forced with local meteorological and river discharge observations. Dissolved inorganic carbon (DIC) and total alkalinity are modeled as scalar quantities and used to calculate pH and aragonite saturation state. Model results show an aragonite saturation horizon at ~20 m that shoals to the surface during winter and sometimes in summer during large freshets from the Fraser River. pH is high (> 8) near the surface in spring/summer/fall and low (< 7.7) below 10 m due to entrainment of DIC-rich water from the intermediate layer. Sensitivity studies suggest a seasonal succession of forcing dominance on surface pH and aragonite saturation state. In spring, pH is strongly anticorrelated to windspeed due to mixing across the large, shallow pH gradient. In summer, pH and river discharge are anticorrelated due to reduced primary productivity near the Fraser River plume. The deepening of the aragonite saturation horizon below the surface in early spring appears to coincide with the onset of the spring diatom bloom, and the summer surface aragonite undersaturation duration is clearly a function of Fraser River discharge. This study demonstrates the importance of local forcing in determining the interannual variability of near-surface pH and aragonite saturation state in the Strait of Georgia.

Session Title

Session S-04A: Frontiers of Ocean Acidification Research in the Salish Sea

Conference Track

Ocean Acidification

Conference Name

Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)

Document Type

Event

Start Date

1-5-2014 8:30 AM

End Date

1-5-2014 10:00 AM

Location

Room 615-616-617

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

Text

Language

English

Format

application/pdf

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May 1st, 8:30 AM May 1st, 10:00 AM

Mechanisms that influence pH and aragonite saturation state in the Strait of Georgia

Room 615-616-617

A 1-D vertical biophysical coupled model is used to investigate the seasonal, interannual, and long-term variability of pH and aragonite saturation state in the southern Strait of Georgia. The model is initialized using casts from local sampling programs, and continuously forced with local meteorological and river discharge observations. Dissolved inorganic carbon (DIC) and total alkalinity are modeled as scalar quantities and used to calculate pH and aragonite saturation state. Model results show an aragonite saturation horizon at ~20 m that shoals to the surface during winter and sometimes in summer during large freshets from the Fraser River. pH is high (> 8) near the surface in spring/summer/fall and low (< 7.7) below 10 m due to entrainment of DIC-rich water from the intermediate layer. Sensitivity studies suggest a seasonal succession of forcing dominance on surface pH and aragonite saturation state. In spring, pH is strongly anticorrelated to windspeed due to mixing across the large, shallow pH gradient. In summer, pH and river discharge are anticorrelated due to reduced primary productivity near the Fraser River plume. The deepening of the aragonite saturation horizon below the surface in early spring appears to coincide with the onset of the spring diatom bloom, and the summer surface aragonite undersaturation duration is clearly a function of Fraser River discharge. This study demonstrates the importance of local forcing in determining the interannual variability of near-surface pH and aragonite saturation state in the Strait of Georgia.