The authors of Ocean Biogeochemical Dynamics aim to provide a theoretical framework for the study of biogeochemical processes in the oceans. They set out an overview of the distribution of major and trace chemicals in the oceans and provide a review of ocean circulation. They adopt a hypothesis-driven approach to tackle some of the key issues, including air–sea exchange, organic matter production and its export to deep water, remineralization and ultimately burial in sediments. They then use the tools developed in earlier chapters to tackle the cycles of carbon, silicon and calcium carbonate and finally discuss the issue of CO₂ and climate.

Those expecting a cosy, qualitative view of the oceans should look elsewhere. This is a seriously quantitative effort! The authors make no apologies; the material is designed for those with a good grounding in maths and physics rather than chemistry and biology. The authors structure the chapters by first identifying the important questions, then examining available data and developing thought experiments and models and ultimately setting up hypotheses or paradigms to be tested. I found this approach to be stimulating and thought provoking. It is an excellent means of getting the message across and in instructing students how problems should be tackled, particularly in ocean biogeochemistry when there are often few data. For example, in the chapter on production, Sarmiento & Gruber develop their arguments regarding the efficiency of the biological pump in the different oceanic biomes by using a combination of observations and modelling. They explain the link between nutrient recycling efficiency and surface nutrient concentration in terms of consumption by phytoplankton, iron supply, light limitation and temperature. They suggest that even in the iron-limited Southern Ocean the system behaves like a large phytoplankton-dominated region, with potentially high export efficiency, rather than a picoplankton-dominated biome with low export efficiency. Why then does experimental addition of iron to surface waters of the Southern Ocean produce only a modest reduction in nutrient concentration? Primarily, the authors argue, because of light limitation. In developing this argument, the authors unravel the literature and provide their own insight to clarify a potentially tricky problem.

In the final chapter, Sarmiento & Gruber discuss the carbon cycle, CO₂ and climate. They identify the Southern Ocean as key in best explaining the variations in atmospheric CO₂ associated with glacial–interglacial cycles. They describe a synthesis hypothesis which links cooling with changes in productivity in the Southern Ocean, which in turn leads to a change in the distribution of nutrients and dissolved inorganic carbon even at low latitude. Ultimately the carbonate compensation depth shoals, leading to drawdown of atmospheric CO₂. Their hypothesis is compelling; their book will stimulate a new generation of oceanographers to prove them right, or wrong! I will certainly be recommending this excellent volume to my students and will no doubt be using it myself very frequently.