An updated synthesis of the observed and projected impacts of climate change on the chemical, physical and biological processes in the oceans

Abstract

The 5th Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) states with very high certainty that anthropogenic emissions have caused measurable changes in the physical ocean environment. These changes are summarized with special focus on those that are predicted to have the strongest, most direct effects on ocean biological processes; namely, ocean warming and associated phenomena (including stratification and sea level rise) as well as deoxygenation and ocean acidification. The biological effects of these changes are then discussed for microbes (including phytoplankton), plants, animals, warm and cold-water corals, and ecosystems. The IPCC AR5 highlighted several areas related to both the physical and biological processes that required further research. As a rapidly developing field, there have been many pertinent studies published since the cut off dates for the AR5, which have increased our understanding of the processes at work. This study undertook an extensive review of recently published literature to update the findings of the AR5 and provide a synthesized review on the main issues facing future oceans. The level of detail provided in the AR5 and subsequent work provided a basis for constructing projections of the state of ocean ecosystems in 2100 under two the Representative Concentration Pathways RCP4.5 and 8.5. Finally the review highlights notable additions, clarifications and points of departure from AR5 provided by subsequent studies.

Marine projections of warming and ocean acidification in the Australasian region

“…How an organism responds to the projected SST changes will depend on the organism (Howes et al, 2015). Once optimum temperatures for which physiological processes are most efficient have been exceeded, these processes are impacted .…”

“…Importantly, changes in primary productivity around Australia would likely have a significant impact on the productivity and return of fisheries, and the biomass of threatened marine animals such as turtles, sharks and seabirds (Brown et al, 2010). It is also anticipated that this warming will adversely impact other key species such as seagrasses and macroalgae that provide key habitats for many species (Howes et al, 2015).…”

“…Nevertheless studies have identified ocean acidification and warming as the two changes in the physical environment that will have the most direct impact on biological systems (Howes et al, 2015). Recent studies have also shown that ocean warming can further exacerbate the impacts of ocean acidification (Kroeker et al, 2013), and equally ocean acidification can exacerbate the impacts of warming (Anthony et al, 2008) on biological systems.…”

Transient Earth system responses to cumulative carbon dioxide emissions: linearities, uncertainties, and probabilities in an observation-constrained model ensemble

“…These may be specific for individual regions and components of the climate system, which includes the atmosphere, hydrosphere, biosphere, and geosphere and their interactions (United Nations, 1992). For example, targets may include bounds for sea level rise, ocean acidification, and ocean warming that threatens marine ecosystem functioning and services (IPCC, 2014;Gattuso et al, 2015;Howes et al, 2015). Ocean acidification is, like global warming, progressing with anthropogenic CO 2 emissions but, unlike global warming, largely independent of the emissions and atmospheric abundance of non-CO 2 forcing agents.…”

“…Ocean acidification in conjunction with warming waters poses large risks to marine species, marine ecosystems such as corals, sea grass meadows, and marine ecosystem services such as tropical fisheries (e.g. Gattuso et al, 2015;Howes et al, 2015). Warming waters affect the aerobic scope of marine organisms and constrain marine habitats (Deutsch et al, 2015;Pörtner et al, 2011).…”