Oceans and Climate Change – Documenting a Decade’s Progress
Those of us involved in ocean and climate research often lose sight of the progress we make. This is because the new techniques in our armoury rapidly become commonplace. The introduction of solid state electronics in the 1970s and of satellite earth observations and supercomputing in the 1990s were such major advances. The past ten years have also seen remarkable progress and that progress has been well-timed as our need to understand the role of the oceans in climate variability and change has become more pressing.
The book, Ocean Circulation and Climate – A 21st Century Perspective, documenting the past decade’s advances was published in November 2013. It’s publication coincided almost exactly with the issuing of the 5th Assessment Report of Working Group 1 of the Intergovernmental Panel on Climate Change (IPCC) – a comprehensive review of our knowledge of the physical climate system and what that knowledge can tell us about future climate change. Together these two publications are a phenomenal body of information.
Climate change is fundamentally about changes in the flow and storage of energy in the Earth’s environment and the oceans are the key element in global energy storage. This has consequences. While the absorption of heat by the ocean slows the rate of change it also implies that change will continue for many centuries and we know that the oceans are warming – the amount of energy they absorb, equivalent to the energy from four Hiroshima nuclear bombs every second, dwarfs all other changes in energy storage in the Earth system.
Observing and modeling the oceans at global scales are together central to making the climate projections needed by politicians and policy makers. Ocean Circulation and Climate – A 21st Century perspective covers in detail the oceans’ role in climate and as such provides essential reading for those who wish, if you will pardon the pun, to delve deeper. The book has 31 chapters written by 76 expert researchers, 8 of whom were contributors to IPCC AR5 including the coordinating lead authors of two IPCC chapters (Ocean Observations, and Sea Level Change). The opening chapter of the book on “The Ocean as a Component of the Climate System” was contributed by the Chairman of IPCC WG1, Thomas Stocker.
The book is the second edition of a book “Ocean Circulation and Climate – Observing and Modelling the Global Ocean” published in 2001 by Academic Press following the conclusion of the World Ocean Circulation Experiment (WOCE), arguably the largest ocean research project ever undertaken. Though WOCE revolutionised our understanding of the ocean and climate what is remarkable, and is documented in the new book, is the enormous advances made since 2001.
One example is the Argo fleet of over 3000 robotic profilers (complemented by new satellite missions) that now provide round-the-clock information on the temperature and salinity of the oceans’ uppermost 2km. The Argo technology was developed during WOCE and the first edition refers to the programme’s potential impact. In the new book its results are featured in no less than 24 chapters! Argo data have inter alia reduced uncertainties in sea level projections (ocean warming was the largest single component of sea level rise over recent decades and is projected to be the largest component during the 21st century, followed by the loss of mass from glaciers). Argo also, surprisingly, provides a global scale rain gauge that is revealing (through changes in salinity distribution) a strengthening of the hydrological cycle. The consequent increases in extremes of rainfall and drought, just as with rising sea level, have profound socioeconomic consequences.
Argo is also starting to provide information on ocean biogeochemistry – essential for understanding the oceans’ role in the global carbon cycle. The oceans are just as important in this regard as the rainforests! However the absorption of carbon dioxide in the ocean, while reducing atmospheric concentrations, has potentially adverse consequences on marine organisms through ocean acidification.
The focus on ocean circulation is important since it covers the transport of heat and other properties by ocean currents. New insights revealed in the 2013 book include previously unknown striations in ocean surface currents and a new ability to predict the fate of ocean debris (including that from the 2011 Japanese tsunami). A monitoring array across the Atlantic at 26°N, in place since 2004, now shows high-frequency variability in ocean heat transport that was unknown at the time of the first edition.
Another highlight in the book is a greater emphasis on the polar regions – sensitive indicators of climate change – with chapters on the marine cryosphere and on the Arctic and Southern Oceans. Since the first edition there has been a complete review of the thermodynamics of seawater and a redefinition of its equation of state. Though this has relatively minor consequences to upper ocean observations it is of significance in the deep ocean and in the formulation of ocean models. Various aspects of ocean modeling are covered in 7 chapters and particularly demonstrate the advances made through increased computer power, improved parameterization of ocean processes and in the assimilation of ocean observations into models and their use in ocean state estimation. Models are essential for the interpretation of, still sparse, ocean observations and of course for the projection of future changes in the oceans and atmosphere.
The first edition rapidly became a standard text that was of enormous value particularly for graduate students embarking on a career in ocean research and the second edition is similarly both comprehensive and accessible. The second edition contains a wealth of new material and the editors and authors wait to hear readers’ and reviewers’ reactions but are proud to have produced a book that highlights many aspects of the growing awareness of the importance of the oceans’ in earth’s climate on timescales ranging from seasons to millennia.
The manner in which the book’s subject matter underpins the work of IPCC was highlighted at a meeting “Climate Change 2013 organized by the UK’s Royal Meteorological Society in London on February 5th 2014.
Ocean Circulation and Climate – A 21st Century perspective is available for purchase on the Elsevier Store. Use discount code “STC3014″ at checkout to save 30% on your very own copy!
Biographical notes on the editors
The book’s editors are Gerold Siedler (centre left) - Germany, Emeritus Professor of Oceanography, University of Kiel, John Gould (right) author of this blog – UK, former Director of the World Ocean Circulation Experiment and of the Argo project, John Church (left) – Australia, world-renowned expert on sea-level change, all of whom, were editors of the first edition. They were joined by Stephen Griffies (centre right) – USA, an expert in ocean and climate numerical modeling and the 2014 recipient of the European Geophysical Union’s Nansen gold medal.
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