Considered one of the phenomena that most affect marine organisms today, ocean acidification was not mentioned by the UN Intergovernmental Panel on Climate Change (IPCC) until its Fifth Assessment Report (AR5), published in 2014. The First Assessment Report was issued in 1990.
According to the AR5 Synthesis Report’s Summary for Policymakers, the ocean has absorbed approximately 30% of the carbon dioxide (CO2) emitted by humans. Since the beginning of the industrial era, the increase in CO2 concentration and dissolution has lowered the pH of the ocean’s surface water and resulted in ocean acidification, the report says.
Ocean acidification is now part of all the IPCC’s climate change scenarios and will be emphasized even more in the Sixth Assessment Report (AR6), scheduled for completion in 2021, and in the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), which the IPCC expects to complete in September 2019, according to marine biologist Jake Rice, member of the Group of Experts for the UN World Ocean Assessment and Chief Scientist of Canada’s Department of Fisheries and Oceans (2006-16).
Rice attended the São Paulo School of Advanced Science on Ocean Interdisciplinary Research and Governance as one of the invited researchers. The event, hosted by the University of São Paulo’s Oceanographic Institute (IO-USP) with FAPESP’s support, took place on August 13-25, 2018, at the Institute for Advanced Studies (IEA-USP).
“There’s a very high level of confidence that ocean acidification has increased. This phenomenon has well-documented effects on marine organisms that depend on calcium carbonate for their calcification process,” Rice said.
“However, the time series of ocean observation data used to estimate the speed and pathway of this phenomenon in recent decades are very short. For ocean acidity in coastal waters, for example, they date from 2005 or slightly earlier.”
He added that models of terrestrial systems project a global fall in ocean pH and an increase in acidification for all greenhouse gas emission and concentration scenarios, albeit with major regional and local variations that are hard to estimate accurately.
The phenomenon will have the strongest effects, both direct and indirect, on the developing countries and tropical islands that depend on marine resources.
The adverse effects of ocean acidification will include changes in the physiology, behavior and population dynamics of marine organisms such as mollusks and will impinge on coral reefs and other marine ecosystems for centuries if CO2 emissions continue at the current pace. Many other effects are poorly understood.
“Ocean acidification illustrates the many challenges we face in ocean science,” Rice said. “We need more data to establish correlations among the physical properties of dynamic systems with biological impacts on ecosystems and society.”
In his view, one of the factors that make ocean science harder than earth sciences is that it is easier to understand the dynamics of terrestrial systems because we live on dry land and can see and directly analyze how these systems work.
“In our efforts to understand the ocean, we must pay more attention to the evidence and less to the perception that it can be understood by analogy or inference from knowledge of the land and its biophysical systems,” Rice said.
Source : By Elton Alisson | Agência FAPESP