Rapid warming and salinity changes in the Gulf of Maine alter surface ocean carbonate parameters and hide ocean acidification

Abstract

A profound warming event in the Gulf of Maine during the last decade has caused sea surface temperatures to rise to levels exceeding any earlier observations recorded in the region over the last 150 years. This event dramatically affected CO 2 solubility and, in turn, the status of the sea surface carbonate system. When combined with the concomitant increase in sea surface salinity and assumed rapid equilibration of carbon dioxide across the air sea interface, thermodynamic forcing partially mitigated the effects of ocean acidification for pH, while raising the saturation index of aragonite ( ) by an average of 0.14 U. Although the recent event is categorically extreme, we find that carbonate system parameters also respond to interannual and decadal variability in temperature and salinity, and that such phenomena can mask the expression of ocean acidification caused by increasing atmospheric carbon dioxide. An analysis of a 34-year salinity and SST time series (1981–2014) shows instances of 5–10 years anomalies in temperature and salinity that perturb the carbonate system to an extent greater than that expected from ocean acidification. Because such conditions are not uncommon in our time series, it is critical to understand processes controlling the carbonate system and how ecosystems with calcifying organisms respond to its rapidly changing conditions. It is also imperative that regional and global models used to estimate carbonate system trends carefully resolve variations in the physical processes that control CO 2 concentrations in the surface ocean on timescales from episodic events to decades and longer.

The role of sand lances (Ammodytes sp.) in the Northwest Atlantic Ecosystem: A synthesis of current knowledge with implications for conservation and management

“…However, projections of future variability and long‐term changes in circulation are uncertain (Brickman et al, 2018). Similarly, acidification trends of Gulf of Maine waters and parts of the greater NWA shelf have so far been masked by the unusually strong temperature and salinity increases (i.e., lower CO 2 solubility and higher alkalinity, buffering capacity; Salisbury & Jönsson, 2018). A reversal of these decadal trends, combined with predicted increases in freshwater input, could lead to a more rapid acidification of NWA coastal shelf waters in the coming decades, as compared to current model predictions for this region (~−0.35 pH units by 2099, Bopp et al, 2013).…”

Time of Emergence of Surface Ocean Carbon Dioxide Trends in the North American Coastal Margins in Support of Ocean Acidification Observing System Design

“…Relatively larger absolute values of ToE obs in the east coast were partly attributed to higher variability (SD detrended ), as the average observed trends were similar for both coasts (1.85∼1.88 µatm year −1 ). However, other decadal trends may play a role, for example warming, salinity changes and enhanced primary productivity act antagonistically to mask the OA signal in the Gulf of Maine and other northeast regions (Salisbury and Jönsson, 2018), and increased upwelling acts synergistically with OA to amplify the observed trend in the west coast (Fennel et al, 2018 and references therein). The area south of 40 • N along the west coast, featured exceptionally short ToE based on both observed and forced trends.…”

“…Some ocean time-series sites are long enough to detect anthropogenic forcing in ocean biogeochemical variables such as CO 2 fugacity ƒ(CO 2,sw ) and pH, apart from natural variabilities (Henson et al, 2016;Bates, 2017). In other systems (e.g., Gulf of Maine Vandemark et al, 2011;Salisbury and Jönsson, 2018), however, detection of OA from atmospheric CO 2 invasion, is complicated by the influence of other factors, such as freshwater input, organic matter cycling, and ocean circulation (Ilyina et al, 2009;Carter et al, 2016).…”

Stable Isotope Analyses of Multiple Tissues of Great Shearwaters (Ardenna Gravis) Reveals Long-Term Dietary Stability, Short-Term Changes in Diet, and Can be Used as a Tool to Monitor Food Webs

“…Environmental disturbances brought about by global climate change can greatly influence ecosystems and can cause species to change behavior, distribution, or abundance, affecting whole food webs [2]. Given the extent of economic activity that takes place in the Gulf of Maine [1,3] and its potential vulnerability to climate change [4,5], understanding how environmental and anthropogenic factors can affect and change food webs in this region is of great importance.…”