To Follow the Water: Exploring the Ocean to Discover Climate
- Dallas Murphy
The ocean covers nearly 71% of our planet, providing food, minerals, energy, transport, even recreation. It is also crucial in governing our climate system. Indeed the 29% of solid land, which depends on the sustained health of the entire environmental system, is arguably itself anchored in the ocean.
In To follow the Water, Dallas Murphy gives the general reader and the specialist an ocean view beyond the confines of the laboratory or computer model. He rolls from topic to topic in a readable and scientifically astute narrative that touches on the oceans' many aspects — from their exploration over the centuries to their current impact on climate — and their study as a quantitative science today.
Fundamental discoveries await oceanographers, but observations are difficult; the oceans are vast and controlled experiments are impossible. I entered physical oceanography decades ago out of curiosity, coupled with the excitement of going to sea. The field has expanded hugely since then: the research is still fun, but it is now more essential than ever to get it right.
In the early days of exploration, European nations competed to find sea routes to Asia around the southern rim of Africa, or to the great unknown to the west. The southern route succeeded; the western route led to gold, to the great misfortune of those who had arrived there earlier. Even then, some explorers were intrigued by ocean currents as a means to speed up their journey, and by the origin of the cool, tropical subsurface water in which they cooled off.
Gradually these explorers morphed into scientists, although sea-going oceanographers still retain an element of the explorer. We are now armed with more sophisticated tools to measure the ocean's fluctuations — from aboard ships, from instruments moored or floating freely in the ocean, and from satellites peering down from above. Considering salt water's high density — granite is only 2.5 times more dense — and its high heat capacity and latent heat, it's no wonder the vast ocean mass has a lock on the climate. Unfortunately, our inability to simulate properly the ocean processes that transfer heat, water and dissolved chemicals undermines the validity of our global climate models. And there is that annoying dab of carbon dioxide that we are so unwisely burning into the atmosphere, half of which ends up acidifying the ocean.
Oceanographers spend many weeks aboard ship, enduring the rolling and pitching that strains brain and belly. Murphy discovered this uncomfortable truth as a technician aboard the Woods Hole Oceanographic Institution's research vessel Oceanus and on two cruises aboard the US National Oceanic and Atmospheric Administration's Ronald H. Brown. He learned that big science, with its multifaceted programmes involving numerous institutions and countries, boils down to a small band of oceanographers tending to arrays of instruments over 24-hour watch schedules.
Murphy focuses on the North Atlantic meridional overturning circulation (MOC) — of which the Gulf Stream is part — only briefly mentioning other areas of the ocean. The MOC causes warm waters from the top kilometre of the ocean to spread into the northern North Atlantic, where they cool and sink to return southwards; in the process, western Europe is warmed. Fear of a breakdown in the MOC in a warming climate is what motivates much of the big science of the North Atlantic. Past climate patterns suggest that the MOC may slow during cool phases, not warm ones, but cause-and-effect issues need to be sorted out and a more global prospective is needed. Will global climate warming shut down the MOC and induce a cooling of northern Europe? I doubt it, but then the rapidly forced, anthropogenic modification of climate may not follow the same course as past natural changes.
Murphy effectively points out that although the ocean sciences are now more important than ever, funding is so inadequate that very few worthwhile projects receive support. Chasing grant money reduces researchers' productive time, and delays advances in understanding the sea; and the clock is ticking. Meanwhile, the public needs to know about the oceans, but oceanographers remain wary of media misrepresentation of their work. Meticulously following the waters of the Gulf Stream into the blue beyond, Murphy's book gets it right.
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Gordon, A. Oceanography fathomed. Nature 449, 407–408 (2007). https://doi.org/10.1038/449407a
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DOI: https://doi.org/10.1038/449407a
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