Biotic and Human Vulnerability to Projected Changes in Ocean Biogeochemistry over the 21st Century

Abstract

Mora and colleagues show that ongoing greenhouse gas emissions are likely to have a considerable effect on several biogeochemical properties of the world's oceans, with potentially serious consequences for biodiversity and human welfare.

Major impacts of climate change on deep-sea benthic ecosystems

“…Future ocean projections for the year 2100 were compiled from all available data generated by Earth Systems Models as part of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change as in Mora et al (2013). A total of 31 Earth System Models from 18 centers in nine countries were collected and multi-model averages of temperature, pH, O 2 and POC flux to the seafloor were reported as the interannual mean projections between 2090 and 2100 (Mora et al, 2013).…”

“…A total of 31 Earth System Models from 18 centers in nine countries were collected and multi-model averages of temperature, pH, O 2 and POC flux to the seafloor were reported as the interannual mean projections between 2090 and 2100 (Mora et al, 2013). Detailed descriptions of the accuracy and precision of multi-model estimates can be found in Mora et al (2013).…”

“…Over the next 84 years, the highest temperature changes are likely to occur at the abyssal seafloor in the North Atlantic, Southern and Arctic Oceans (Mora et al, 2013) (Table 2; Figure 2). Bathyal depths are also likely to experience increasing temperatures (Soltwedel et al, 2005); Mora et al (2013) modeled increases of 3.6, 4.4 and 3.7°C in the Pacific, Atlantic, and Arctic Oceans (e.g., Barents and Kara Sea), with lower temperature increases in the Indian and Southern Oceans (e.g., at sites of deepwater formation in the Weddell Sea) (Table 2; Figure 2) by 2100. These predictions of temperature change are in alignment with evidence that the deep Greenland Sea has warmed by 0.7°C since the 1950s (~ 0.01°C yr -1 ; Somavilla et al, 2013).…”

“…Continued use of fossil fuels into the 21st century is predicted to lead to atmospheric CO 2 levels > 900 ppm by 2100 (under Representative Concentration Pathway (RCP) 8.5; Meinshausen et al, 2011), though the precise level is highly dependent on the emission scenario (Pachauri et al, 2014). These rising atmospheric greenhouse gas concentrations have led to an increase in global average temperatures of ~ 0.2°C decade -1 , much of which has been absorbed by the oceans, whilst the oceanic uptake of atmospheric CO 2 has led to major changes in surface ocean pH (Levitus et al, 2000(Levitus et al, , 2005Feely et al, 2008;Hoegh-Guldberg and Bruno, 2010;Mora et al, 2013;Roemmich et al, 2015). The deep sea has experienced dramatic changes in physical and chemical variables in the geological past.…”

“…Despite emerging evidence that climate-driven changes in deep-sea environmental conditions may perturb the functioning of oceanfloor ecosystems (Danovaro et al, 2001;Smith et al, 2007Dunlop et al, 2016;, our understanding of the extent to which projected physical and chemical changes will lead to deleterious ecological consequences is still very poor (Philippart et al, 2011). Given that deep-sea ecosystems are vitally important to the Earth system (Danovaro et al, 2014) and are at considerable risk from ongoing climate change (Mora et al, 2013;Jones et al, 2014;Levin and Le Bris, 2015), our goal in this paper is to understand and predict the nature and consequences of climate change at the deep seafloor until 2100. To this end, we describe the present status of four major environmental variables at the seabed that are likely to be altered by increased CO 2 emissions to the atmosphere: temperature, oxygenation, pH and food supply (or POC flux).…”