Sir Nicholas Shackleton

Earlier stages show the slowly evolving nature of glaciation (and the intervening interglacials) on the earth. Nick teamed up with Neil Opdyke, a paleomagnetist who was able to recognize (and date) reversals of the earth’s magnetic field, to provide a timescale for these changes in oxygen isotopes, and this provided a chronology that could then be used to understand the frequency of glaciations and rates of change. Once a fairly reliable timescale was established, it soon became apparent that there had been regular sequences of glaciations and interglaciations that were related to orbital forcing (changes in the earth’s position in relation to the sun, as elaborated by Milankovitch). This was described in a landmark paper in Science (1976) “Variations in the earth’s orbit: pacemaker of the ice ages”, co-authored with colleagues Jim Hays and John Imbrie. From this many more studies of orbital forcing, extending far back beyond the Quaternary period also evolved from the marine oxygen isotope stratigraphy. In particular, the CLIMAP (1981) project emerged, in which paleoceanographers mapped ocean conditions at the height of the last glaciation, by identifying in each sediment core the position where the isotopes in benthic forams were most enriched (indicating maximum ice on the continents). While many of the initial CLIMAP conclusions have been substantially revised, Shackleton’s isotope chronology remains as an essential tool in understanding earth history.

Having identified a universal chronometer for continental glaciation—not in the moraines and outwash deposits that provide the direct evidence of former ice sheets, but far away in the deep ocean basins—researchers were then able to better understand the history of other terrestrial records, such as the vast loess (wind-blown silt) deposits of China, and the emerging ice core records from Antarctica and Greenland. Furthermore, since the isotopic record in the oceans registered ice growth and decay on land, it effectively provided a proxy for sea-level changes that could be checked with sea-level terraces from areas where the land had risen (such as on the Huon Peninsula of New Guinea, and in Barbados), preserving a record of past sea-level changes in the coral reefs now exposed on land. By comparing the reef-based sea-level history with the benthic foram-based record, Shackleton (with colleagues John Chappell and others) was able to assess the extent to which deep ocean temperatures may have changed over time, which would have confounded the simple paleoglaciation index he originally formulated. Shackleton subsequently argued that changes in glaciation could not be fully explained by orbital forcing, and that feedbacks involving carbon dioxide must have played a critical role, thereby highlighting the importance of changes in the concentration of greenhouse gases in the atmosphere, in the past and in the future.

Nick Shackleton’s research, arising from his original Ph.D. thesis on isotopic variations of tiny marine organisms, had an enormous impact on earth sciences. He had the insight to understand the implications of his measurements and they literally transformed how we now view earth history. For his discoveries he received many honors and awards. He was a Fellow of the Royal Society, a Foreign Member of the U.S. Academy of Sciences, a Fellow of the American Geophysical Union, and numerous other societies also honored him. He was knighted for his “services to science”; with Willi Dansgaard (who made similarly far-reaching studies of oxygen isotopes in precipitation and applied these to ice cores) he received the Crafoord Prize (considered as earth sciences’ “Nobel Prize”); he was also awarded Japan’s Blue Planet Prize, the Milankovitch Medal, and most recently the Vetlesen Prize.

Though he always considered himself, “just a geologist”, Nick had many other talents, most notably in music. He was an accomplished clarinet player and had a passionate interest in the history of that instrument. He was considered a world expert for his knowledge of antique clarinets and he had his own unique collection. At Cambridge University, where he spent his entire career, Nick gave lectures on Quaternary geology and paleoclimatology, but he also taught the physics of music. Perhaps it was his knowledge of harmonics that played a critical role in his understanding of orbital forcing and its impact on earth history. At the tri-ennial ICP conference, Nick would always organise a Paleo-musicology concert where the many musically talented scientists (and occasionally their more-talented children) would entertain the rest of us. Nick was a true Renaissance man and he leaves a very important legacy to both musicology and the earth sciences. Besides all this, he was a nice guy and an inspiration to all who came into contact with him.

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7 comments on this post.
  1. Matt:

    Well, thanks Ray for explaining the oxygen isotope tool, and by extension I understand how carbon isotope measurements are used.

    You then sent me off looking as sea level and temp; and that, leads of course. to the younger-dryas event. My “google scholar” search informs me that we don’t yet understand the younger-dryas, but that event seems to be the mark the initiation of the holocene period.

    Younger-dryas seems like an aborted attempt to restart the glacial cycle, but lacked sufficient forcing function, so the switch did not flip (the oceans circulation (or bedrock) had an extra moment to equilibriate, robbing the glacial cycle of its momentum. In fact, a few hundered years earlier there seemed to be another abortive attempt.

    After the younger-dryas event, CO2 levels no long follow the familiar relationship it had in past cycles.

    Comparison with previous cycles (Vostok Ice Core) leads me to conclude the cycle is especially dependent on the CO2 forcing fuction right at the cycle midpoint.

    Is there thought that successive glacial cycles have sequestered more and more carbon, eventually robbing the cycle of co2 forcing?

  2. SteveF:

    Yes, it was a very sad loss. Reading a Shackleton paper was always an inspiration for those of us training in the palaeoclimate field (though I’m still trying to get to grips with his 2000 Science paper!). His recent work on MIS 5e off the coast of Spain was particularly interesting and was of considerable assistance in my MSc research. Coming not long after the death of Gerard Bond, it was a real blow to the Quaternary Science community.

    I collected a few of the obituaries in the British press and there is a tribute website over at the Godwin Lab:

    http://education.guardian.co.uk/obituary/story/0,,1708276,00.html

    http://www.timesonline.co.uk/article/0,,60-2016945,00.html

    http://www.quaternary.group.cam.ac.uk/

  3. Matt:

    Dr. Shackleton, a great man, who might, historically, be listed as one of the men who saved humanity.

    But I am still a little hysterical.

    I think we have a much bigger problem. I don’t think we can wait 100,000 years for the next orbital period and nature wants to recyle the biosphere through the glacial period. We are sitting in the hot house, and the carbon budget is not off by 6 gigatons per year, but more like 12 gigatons per year. At these temperature we likely have a much greater total flux than the biosphere can support indefinitely, much less a net flux.

    We may need a solution on a much grander scale, like disenfecting the soils and killing of the soil microbes in a mass extinction. Otherwise, project the biosphere ahead at these temperature for 100,000 years, and it does not seem too pretty to me.

  4. David B. Benson:

    Thank you for the helpfully informative obit.

  5. Persa:

    It is sad news, and a significant loss. I met Sir Nick at a conference in Cambridge. At first I was afraid to talk to him because of his lofty reputation and title, but he was very kind. He will be missed.

  6. raypierre:

    Once out of nature I shall never take
    My bodily form from any natural thing
    But such a form as Grecian goldsmiths make
    Of hammered gold, and gold enameling
    To keep a drowsy emperor awake
    Or set upon a golden bough to sing
    To lords and ladies of Byzantium
    Of what is past, or passing, or to come.
    — W.B. Yeats

  7. Climate Progress » Blog Archive » Sea levels may rise 5 feet by 2100:

    […] Here is the entire abstract from the article — note that the Eemian is also called “Marine Isotope Stage 5“: […]