Harry Elderfield (1943–2016) Geochemist Who Deciphered Chemical Signatures in the Modern and Ancient Oceans

COMMENT OBITUARY Harry Elderfield (1943–2016) Geochemist who deciphered chemical signatures in the modern and ancient oceans. enry ‘Harry’ Elderfield showed how years, Elderfield explored the role of vents the distributions of chemicals in in ocean chemistry, as well as fluid flow seawater and sediments can reveal through the sea floor.) Hthe ocean’s role in historical climate change. Around the same time, Elderfield and Elderfield, who died on 19 April, was Edmond, who then was at the Massachusetts born in 1943, at the height of the Second Institute of Technology (MIT) in Cambridge, CAMBRIDGE UNIVERSITY World War, in North Yorkshire, UK. A arranged sabbaticals in each others’ labs. But few days before his birth, his father, Henry, as a result of slightly haphazard planning they was reported missing in action, presumed never overlapped in the same place. At MIT, drowned, a loss that may have contributed Elderfield instead spent much of his time to Elderfield’s draw to the oceans as well as to with the palaeochemist Edward Boyle, who the past. After obtaining a degree in chem- was then trying to relate the chemistry of the istry from the University of Liverpool, UK, shells of foraminifera, single-celled organ- in 1965, he completed a postdoctoral fellow- isms known as protists, to the chemistry of ship at Imperial College London, in 1969, the seawater in which they lived. and started a lectureship at the University of In the shell material, foraminiferal calcite, Leeds, UK, even before completing his PhD. trace metals of similar size sometimes replace In 1977, Elderfield headed to the Uni- calcium; even trace anions can take the place versity of Rhode Island in Kingston for a of the carbonate ion. Elderfield pioneered sabbatical year. There he met geochemists the exploitation of these ‘mineralogical mis- Gary Klinkhammer, John Edmond and takes’ to gain insight into past ocean compo- Wallace Broecker. Discussions with these sitions. He established, for instance, that the scientists would have a major influence on temperature of the ocean at the time that the the research questions that he later pursued. foraminifera formed can be inferred from the Back at Leeds, Elderfield’s laboratory isotopes that decay radioactively over time magnesium–calcium ratio in shells. This ratio technician, Mervyn Greaves, was told to could be used to solve marine geochemical provides a way to distinguish between the make himself useful in the lab of another puzzles. With Martin Palmer, who had been shifts in oxygen isotopes in the shells caused faculty member, Chris Hawkesworth. a student of Elderfield’s at Leeds, he developed by changes in ocean temperature from those Hawkesworth had established a way to ana- the strontium isotope curve for seawater for caused by changes in the size of Earth’s polar lyse rare-earth metals — a group of 17 ele- the past 75 million years. Analysing the ratios ice sheets. Ultimately, Elderfield helped to ments — in 1-gram rock samples. Elderfield’s of strontium isotopes taken from sediments reveal the independent history of changes biggest scientific splash came when he and of known age, the pair mapped the changes in global temperature from the waxing and Greaves applied a modified version of this in the isotopic ratio in the ocean over time. waning of Earth’s ice sheets over thousands method to 50-litre samples of seawater and This isotopic curve, recorded globally in or millions of years. made the first measurements of the tiny con- limestone, shows the shifting effects of con- Harry was a warm, playful, family man. centrations of ten rare earths from samples tinental weathering and hydrothermal vents. He had a mischievous sense of humour and collected from the North Atlantic. They were These sea-floor features spew spectacular a taste for fine art, music, wine and unusual present in picomolar amounts (on the order plumes of geothermally heated water and spirits. He also had an incredible knack of of 10–12 moles per kilogram). chemicals into the ocean, and are the major teasing sense out of disorder — or in his Elderfield established how the composi- suppliers of strontium to the ocean. Stron- words, of finding the “really interesting” tion of rare earths in a sample, and the specific tium isotope stratigraphy, a term coined by trends in “unascribable scatter”. properties of the elements, could be used to Elderfield to describe the mapping of stron- I was one of his PhD students in the 1990s. identify different water masses — deep water tium isotopes in layers of rock, is now widely On one tumultuous day I discovered that bodies from different parts of the ocean that used to date sediments. It has also proved another group had reported findings similar have distinct physical properties. He also pre- useful for climate scientists. Weathering to those at the heart of my PhD. Harry dis- dicted — correctly — that these signatures pulls carbon dioxide out of the atmosphere sipated my fears with one sentence: “It just could be extracted from the ocean sediments and vents release the gas, so the strontium shows you are doing exciting science.” After covering the sea floor and used to track how isotope curve provides a proxy for tectonic a pause and a wry smile, he added, “But let’s ocean circulation has changed over time. (The processes that are crucial to the carbon cycle. do it better”. ■ composition of rare earths in the sediment of In 1985, Elderfield’s group participated in a particular geological age reflects the compo- a cruise that produced the first photographs Rosalind E. M. Rickaby is professor sition of the elements in the ocean water at the of a hydrothermal vent called the TAG vent of biogeochemistry at the University of time that the layer was formed.) site (P. A. Rona et al. Nature 321, 33–37; Oxford, UK. Harry Elderfield was her PhD In 1982, Elderfield moved to St Catharine’s 1986). This was the first vent discovered in supervisor at the University of Cambridge, College at the University of Cambridge, UK. the Atlantic Ocean or indeed on any slow- UK, from 1995 to 1999. Here he was one of the first to realize how spreading mid-ocean ridge. (In subsequent e-mail: [email protected] 322 | NATURE | VOL 533 | 19 MAY 2016 ©2016 Mac millan Publishers Li mited. All ri ghts reserved. .

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