title: Century-scale trends and seasonality in pH and temperature for shallow zones of the Bering Sea.
abstract: No records exist to evaluate long-term pH dynamics in high-latitude oceans, which have the greatest probability of rapid acidification from anthropogenic CO2 emissions. We reconstructed both seasonal variability and anthropogenic change in seawater pH and temperature by using laser ablation high-resolution 2D images of stable boron isotopes (δ(11)B) on a long-lived coralline alga that grew continuously through the 20th century. Analyses focused on four multiannual growth segments. We show a long-term decline of 0.08 ± 0.01 pH units between the end of the 19th and 20th century, which is consistent with atmospheric CO2 records. Additionally, a strong seasonal cycle (∼ 0.22 pH units) is observed and interpreted as episodic annual pH increases caused by the consumption of CO2 during strong algal (kelp) growth in spring and summer. The rate of acidification intensifies from -0.006 ± 0.007 pH units per decade (between 1920s and 1960s) to -0.019 ± 0.009 pH units per decade (between 1960s and 1990s), and the episodic pH increases show a continuous shift to earlier times of the year throughout the centennial record. This is indicative of ecosystem shifts in shallow water algal productivity in this high-latitude habitat resulting from warming and acidification.
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany; jfietzke@geomar.de.
authors.forename: Jan
authors.initials: J
authors.lastname: Fietzke
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany; Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, United Kingdom; Institute of Marine Sciences, University of Portsmouth, Eastney, Portsmouth, P04 9LY, United Kingdom;
authors.forename: Federica
authors.initials: F
authors.lastname: Ragazzola
authors.affiliation: Department of Earth Sciences, University of Toronto, Mississauga, ON, Canada L5L 1C6; and.
authors.forename: Jochen
authors.initials: J
authors.lastname: Halfar
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany;
authors.forename: Heiner
authors.initials: H
authors.lastname: Dietze
authors.affiliation: Department of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, United Kingdom;
authors.forename: Laura C
authors.initials: LC
authors.lastname: Foster
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany;
authors.forename: Thor Henrik
authors.initials: TH
authors.lastname: Hansteen
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany;
authors.forename: Anton
authors.initials: A
authors.lastname: Eisenhauer
authors.affiliation: School of Marine Sciences, University of Maine, Walpole, ME 04573.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Steneck
keywords: boron isotopes; crustose algae; isotope imaging; laser ablation ICP–MS; ocean acidification