John T. Andrews
University of Colorado
2016 Penrose Medal
Presented to John T. Andrews
Citation by Peter U. Clark
John T. Andrews is a preeminent geoscientist whose outstanding original research contributions in geology embody the very essence of a Penrose Medalist. In the course of over 50 years of research, service, and mentoring that continues to this day, John has not only revolutionized our understanding of the history and dynamics of the Pleistocene North American ice sheets, but has left a lasting legacy in his mentoring of more than 75 scientists. His more than 300 publications span the fields of glacial geology, stratigraphy, paleomagnetism, geodynamics, geochronology, paleoceanography, and paleoclimatology, and many have challenged existing paradigms and provided fundamental insights into some of geology’s biggest questions. In particular, John’s body of work has fundamentally changed our understanding of the former Pleistocene ice sheets which had such a profound influence on the Earth system.
Up until the start of John’s research in the Canadian Arctic, our understanding of the North American Laurentide Ice Sheet was largely based on decades of work in the Great Lakes region that, while only reflecting a small sector of the ice sheet, was generally accepted as being representative of the ice-sheet history as a whole. John’s subsequent work in the central and eastern Canadian Arctic conclusively demonstrated otherwise, with his detailed field work revolutionizing our understanding of the Laurentide Ice Sheet. Why is this work of significance? Ice sheets, past and present, represent a key component of the global climate system, and variations in their size have been the dominant control on global sea level for much of Earth history. Understanding how ice sheets (present and past) respond to and amplify climate change thus represents one of the grand challenges in the geological sciences. John’s wide-ranging research on the Laurentide Ice Sheet has continually defined the field on this important topic, and much of what we know about the history and dynamics of the ice sheet can be traced back to his contributions.
Among John’s many contributions, several are particularly noteworthy in representing a fundamental contribution in their own right, and each continues to occupy center stage of geoscience research at the international level.
(1) His benchmark work in the 1960s and 1970s on developing records of relative sea level change clearly revealed the isostatic response to loading by the Laurentide Ice Sheet. At the same time, John developed the first history of changes in the area and thickness of the ice sheet during the last deglaciation. This work formed the geological underpinning for research done in collaboration with Richard Peltier to derive the rheology of the solid Earth as well as to develop a forward model to predict relative sea level histories around the globe. Such models have now become central in evaluating our understanding of Earth’s rheology as well as in understanding past, present, and future regional sea-level variability.
(2) His 1973 analysis of the energy budget required to deglaciate the Laurentide Ice Sheet demonstrated that there was a substantial energy deficit from insolation forcing alone, identifying, for the first time, the importance of ice-sheet instabilities and feedbacks in causing the rapid deglaciation. This was the first demonstration of the 100-kyr problem that continues to challenge the paleoclimate community, and has implications that continue to resonate today over our understanding about the future of Earth’s present ice sheets.
(3) His work with graduate student Molly Mahaffy in the 1970s led to the first three-dimensional numerical ice-sheet model, the basic components of which remain the standard for many ice-sheet models today. At the same time, John and colleagues addressed the question of the last glacial inception, including using the ice-sheet model to first demonstrate that Milankovitch forcing alone was insufficient to initiate ice-sheet growth at the rate inferred from the geological record, implying the need for additional feedbacks on that forcing.
(4) His work with colleagues in the 1980s in applying novel geochronological methods to date deposits beyond the range of radiocarbon and in using sediment tracers to document ice-sheet scale flow patterns pointed to a highly dynamic ice sheet where centers of mass may have rapidly migrated as the interior of the ice sheet collapsed several times during the last glaciation. The fact that such ice-sheet behavior may exist shook the very foundations of then current understanding, and provided geological documentation of a potential behavior that is now of widespread scientific and public concern.
(5) His pioneering work in examining the marine record from the North Atlantic Ocean led to new understanding of ice sheet-ocean interactions that contribute to the abrupt climate changes on millennial timescales. John recognized early on that continuous archives of ice sheet-ocean interactions would be preserved in sediment records on glaciated marine shelves, an archive largely ignored by paleoceanographers up to that point, and thus resolve some of the problems encountered in trying to reconstruct the glacial history of the Laurentide Ice Sheet from land-based evidence. This effort in the late 1980s and early 1990s led to the recognition that Heinrich events reflect partial collapses of the Laurentide Ice Sheet, a startling discovery that remains a primary focus of research in the paleoclimate and paleoceanographic community.
Perhaps John’s most enduring legacy has been the more than 75 graduate students he supervised, most of whom now populate our profession in academia, government, or industry. He was an early advocate of a gender-neutral graduate program and has mentored a large number of exceptional female graduate students. His graduate supervision and generous sharing of ideas has inspired the careers of many in the field today, and created a community of educators and researchers who carry on his legacy.
John Andrews has also served the community selflessly, chairing the Quaternary Geology and Geomorphology Division of GSA and the American Quaternary Association, as well serving on as many national and international committees. In honor of his scientific contributions, John has received the University Medal from the University of Colorado, he has been elected Fellow of GSA, AAAS, and AGU, he received the Distinguished Career Award from QG&G Division of GSA, and he holds numerous other national and international honors.
2016 Penrose Medal — Response by John T. Andrews
When I read my email and learned that I had been awarded the Penrose Medal, I was shocked and also a little doubtful about the wisdom of the committee! It is indeed an unexpected honor, and I would like to express my appreciation to Peter Clark, Giff Miller, Dick Peltier, Richard Alley, and Tom Cronin for submitting my name for consideration and for the kind words of the citation. I am also proud to be a representative of the Division of Quaternary Geology and Geomorphology, as I have been a member of the GSA and this Division since 1968.
I came from a small industrial (mining) town (Millom, pop. 7000) on the Cumberland (UK) coastal fringe, with the Irish Sea at our doorstep and the fells and mountains of the Lake District only 1 km to the east. Having been brought up in the North of England during WWII and the subsequent dire post-War years then my adaption to Arctic climate and field conditions was easy!
I attended the University of Nottingham where, in addition to playing rugby, I learned about glacial geology, glaciology, meteorology, oceanography, and plate tectonics—amongst other things. I went on to attend McGill University and spent a year at the Sub-Arctic Research Station as a weather observer—my first paper was on the strength of lake ice. McGill in the early 1960s was a center for Arctic research, and this focus was strengthened by the presence of the Arctic Institute of North America being literally across the road from the McGill Campus in Montreal. This was a time, undoubtedly driven by the Cold War, of a tremendous increase in the exploration and mapping of the Canadian Arctic. Coincidentally, it was also a time that saw the widespread application of radiocarbon dating to the establishment of the late Quaternary history of the North American Ice Sheets. In 1961, I was offered a position with the Canadian government to work on Baffin Island. This was an exciting time for Quaternary research, and it saw the resurgence of entities such as the “Friends of the Pleistocene” and INQUA.
In 1968, I had taken a faculty position at the University of Colorado Boulder in the Department of Geological Sciences with an association with the Institute of Arctic and Alpine Research but continued my research interests that had its roots in my Canadian experiences. The combination of extensive field mapping, aided by air photo mapping, and radiocarbon dating of sediments that could be associated with ice margins led to two isochrone maps of the deglaciation of North America (Bryson et al, 1969, and Prest, 1969); for the first time, these maps showed the pronounced asymmetry of the pattern of deglaciation. In 1970, I was able to use my own work and that of colleagues to reconstruct the postglacial glacial isostatic recovery of eastern North America. These two data gathering exercises gained additional importance when I was introduced to a visiting Canadian physics post-doc, Dick Peltier, and we embarked on an ambitious effort to model the 3-part “forward problem.” This involved the reconstruction of changes in the area and volume of the ice sheets (ICE-1), the development of a data base of relative sea level changes from within and outside the glacial limits, and an Earth rheological model. ICE-I has of course evolved as new data and new insights have been obtained and it now stands at ICE-6. My interests at this time were focused on how, where, and how fast do large ice sheets grow and collaboration with graduates Molly Mahaffy and Larry Williams were important steps in trying to see if we could model the rate of sea level fall during Marine Isotope 5 stadials—although we invoked massive lowering of snowlines and large positive mass balances we could not simulate the rate of ice sheet growth. This was also the time when Giff Miller and I were trying to define the seaward extent of the Laurentide Ice Sheet across Baffin Island and engaged in the “Big Ice” versus “Little Ice” debate with George Denton and Terry Hughes. In1982 my thoughts on the reconstruction large ice sheets were summarized in the first paper of the new journal Quaternary Science Reviews.
The focus on ice sheet growth shifted in the 1980s as I worked with Bill Shilts, Giff Miller, Harvey Thorleifson, and Phil Wyatt on the chronology of events recoded in the Quaternary sequence of the Hudson Bay Lowlands—at the center of the former Laurentide Ice Sheet. In order to test whether Hudson Bay had become ice-free during MIS3 I decided that an answer might lie offshore in cores from the Labrador Sea. Hudson Bay and Strait are floored with Paleozoic limestone and we could reconstruct the ice sheet history by documenting and dating changes in the detrital carbonate (DC) content in marine cores. Two Canadian-based researchers (Chough and Aksu) had already described several DC units in cores, but their importance in terms of the abrupt changes in the dynamics of the Laurentide Ice Sheet took on new meaning with the investigation into “Heinrich” events which Kathy Tedesco and I described in a paper spearheaded by Gerard Bond in 1992.
In the 1990s, I was able to participate in cruises to the East Greenland fjords and shelf, including an episode with an iceberg and CSS Hudson, and started a long-term project of collaboration with researchers in Iceland with successful cruises on the Bjarni Saemundsson, and investigations into the late glacial history of the Greenland Ice Sheet with collaboration of colleagues from Canada, UK, Denmark, and Germany.
Basically, it has been fun, and I have been fortunate to be in the right place at the right time and have met and worked with good people, and I hope that they will forgive the absence of specific name recognition. However, I would like to specifically mention the scientists and staff of the Geological Survey of Canada–Atlantic Division for their support over three decades, and to Dennis Eberl of the U.S. Geological Survey for giving me a set of “tools” to keep me busy during the so-called “retirement.” However, I could not have undertaken the various projects without the support of many people. I would like to thank my wife Martha and family; my early mentors (Cuchlaine King, Jack Ives, John Fyles, Alexis Dreimainis, and Vic Prest); and my colleagues at the University of Colorado (Bill Bradley, Pete Birkeland, Pat Webber, Nel Caine, Roger Barry, Giff Miller, James Syvitski, and Anne Jennings). I have been fortunate to have a large number of graduate students who have taught me a great deal about Quaternary science—they know who they are.
I will end by thanking Baffin Island, Arctic Canada, and its indigenous peoples for providing a rich treasure trove of Quaternary puzzles that have provided me, my colleagues, and graduate students many years of enjoyment, but also for the magnificence of its landscapes and the tranquility it brought.