Changes in oceans may already be irreversible
August 11th, 2009 by Jim JustHuman activities are releasing gigatonnes of carbon to the Earth’s atmosphere annually. Consequently, oceans are changing physically, in some ways at unprecedented rates – and biological change is likely to be commensurately quick. That’s the conclusion of a new study published in Current Biology titled “Impacts of Climate Change on Marine Organisms and Ecosystems” (a summary is also available).
Direct consequences of cumulative post-industrial emissions include increasing global temperature, perturbed regional weather patterns, rising sea levels, acidifying oceans, changed nutrient loads and altered ocean circulation. These and other physical consequences are affecting marine biological processes from genes to ecosystems, over scales from rock pools to ocean basins, impacting ecosystem services and threatening human food security.
Study authors Andrew S. Brierley and Michael J. Kingsford note that oceans play an essential roles in planetary function and provision of human sustenance. Our grand challenge is to intervene
before more tipping points are passed and marine ecosystems follow less-buffered terrestrial systems further down a spiral of decline.
What needs to be done to save the oceans? The answer is simple:
The principal brake to climate change remains reduced CO2 emissions.
As the authors point out, when Earth formed about 4.5 billion years ago there were no oceans. The surface water that accumulated in the ocean basins have been the “reaction chamber” for the development of life on Earth. They play a fundamental role in the ongoing evolution of the planet’s climate. The oceans’ life forms are not just passive occupants that are impacted by physical change. They make active and climate-influencing contributions to planetary function. For example, marine organisms have important roles in the cycling of carbon (the 
biological pump
), nitrogen and other key elements, turbulent mixing and the production of cloud condensation nuclei. There are numerous interactions between climate, physical oceanographic processes and marine biology that are ignored at our peril.
The authors warn:
At current emission rates it is possible we will pass the critical level of 450 parts per million CO2 in the atmosphere by 2040. That’s the level when, it is generally agreed, global climate change may become catastrophic and irreversible. At that point we can expect to see the loss of most of our coral reefs and the arctic seas.
The climate is currently warming faster than the worst case known from the fossil record, about 56 million years ago, when temperatures rose about 6 degrees over 1000 years. If emissions continue it is not unreasonable to expect . . . warming of 5.5 degrees by the end of this century.
It may already be too late to avoid major irreversible changes to many marine ecosystems. As history has shown us, these marine-based changes could have major earth-system consequences.