Projecting ocean acidification impacts for the Gulf of Maine to 2050

Abstract

Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.

Effects of ocean acidification on larval Atlantic surfclam (Spisula solidissima) from Long Island Sound in Connecticut

“…Wang et al (2017) observed a decrease of 0.01 in Ω aragonite for every 1 µmol/kg increase in dissolved inorganic carbon (DIC), similar to what has been observed in the open ocean (Bates et al, 2014). Recently, an oceanographic glider, an autonomous underwater vehicle, was used off the coast of New Jersey to measure subsurface pH levels, which ranged from 7.91 to 8.20, and to measure Ω aragonite , which ranged from 1.5 to 2.2 with higher readings at the surface (Saba et al, 2019).…”

“…Movement of populations of Atlantic surfclam northward and into deeper water can be attributed to warming temperatures . Limited ρCO 2 data, combined with modeling results, indicate that decreases in pH and Ω aragonite occur in the areas to which Atlantic surfclam are moving (Wang, 2016;Saba et al, 2019;Friedland et al, 2020;Siedlecki et al, 2021). This study focused on only the ρCO 2 levels predicted for the RCP 6.0 and RCP 8.5 scenarios; we did not look at the role of increasing temperature.…”

Climate impacts on the Gulf of Maine ecosystem

“…We relied on an ensemble of high-resolution projections for ocean conditions in our region (Brickman et al, 2021). This article complements other Gulf of Maine 2050 scenario papers on ocean acidification (Siedlecki et al, 2021) and sea level rise and storms (Chisholm et al, 2021).…”

Empowering hope-based climate change communication techniques for the Gulf of Maine

“…This rapid warming prompted the Gulf of Maine 2050 Symposium in November 2019. The Symposium asked participants to envision the future of the Gulf of Maine as it responds to three drivers of climate change: temperature and circulation, coastal and ocean acidification, and sealevel rise (Brickman et al, 2021;Chisholm et al, 2021;Siedlecki et al, 2021). For each of these drivers, current understanding of these drivers and how conditions are likely to change over the next 30 years were synthesized.…”