Lamont-Doherty Earth Observatory, Palisades, N.Y.
Gerard C. Bond was awarded the Ewing Medal at the AGU Fall Meeting Honors Ceremony, which was held on 10 December 2003, in San Francisco, California. The medal honors “significant original contributions to the scientific understanding of the processes in the ocean; for the advancement of oceanographic engineering, technology, and instrumentation; and for outstanding service to marine sciences.”
Citation
“In 1991, a set of curious white layers in Deep Sea Drilling Project core 609 captured Gerard Bond’s attention, launching him on the path that has resulted in this award. He confirmed Hartmut Heinrich’s assessment that these layers consisted of ice-rafted debris dropped by the melting of armadas of icebergs from eastern Canada. He looked at the ice-borne entities in the glacial sediment between the Heinrich layers and discovered that the ratio of red (i.e., iron-stained) grains to total grains swung between limits of about 17 and about 4%. The spacing between the maxima of this quasi-cycle averaged 1500 years. Extending his measurements into the Holocene, Gerard found that despite the dramatic drop in grain abundance, the swing in grain composition continued with no significant change in limits or duration. Bond reasoned that as the sources of the red grains were located largely in the Arctic, the red-grain maxima represented cold episodes. The payoff came when, working with Bernd Kromer and Jurg Beer, he demonstrated that the red-grain maxima corresponded to times of maximum production of both 14C and 10Be. Because the production rate of these cosmogenic isotopes is modulated by the heliomagnetic field, this suggests that Earth climate is perturbed by changes in the Sun’s radiation output. If correct, this finding raises difficult questions. How is it that tiny changes in solar irradiance associated with sunspot activity have led to 1 degrees C swings in Holocene temperature? Were the jumps in glacial climate from one state to another paced by the Sun?
“In 1962, after graduating from Capital University, Gerard went to Alaska to study glaciers with Troy Pewe. More interested, though, in geology around the glaciers, he did his master’s thesis on regional Alaskan geology and continued that work for his Ph.D. at the University of Wisconsin. He taught geology first at Williams College, and later at the University of California at Davis. After moving to Lamont in 1980, he began fieldwork that led to his reconstruction of an early Paleozoic supercontinent. In the late 1980s, Gerard used a technique invented by Michelle Kominz to test for Milankovitch forcing of cycles in Paleozoic and Mesozoic stratigraphic sequences. To test this methodology, he produced with Michelle digital grey-scale records of a North Atlantic deep sea core (DSDP 609). He sent me a proposal he and Michelle had submitted that contained photos of core 609. I pointed out to Gerard that the color banding on Milankovitch timescales was punctuated by distinct, narrow dark bands that might be the marine imprint of Dansgaard/Oeschger cycles. The rest is history.
“I could not be more pleased that Gerard Bond is receiving this award. He is a gifted researcher who followed his intuition that locked in the record of ice-rafted rock fragments is a treasure trove of information. Nature carefully guarded her secrets, and only with enormous effort was he able to pry them loose. Maurice Ewing would, I’m sure, fully share my opinion, for Gerard Bond walks very close to Doc’s footprints.”
—WALLACE S. BROECKER, Lamont-Doherty Earth Observatory of Columbia University, Palisades, N.Y.
Response
“Thank you for those generous words, Wally, and I thank the AGU committee for this splendid award named in honor of Lamont’s founder and first director.
“I never met Maurice Ewing, but my office is near one of his greatest legacies: the Lamont-Doherty Deep Sea Sample Repository. Over the years this library of some 8000 deep-sea cores and dredge hauls has helped launch or advance the careers of hundreds of students and professionals including myself. Indeed, the first convincing match of ocean surface temperatures to the full series of dramatic Dansgaard/Oeschger temperature variations above Greenland came from our group’s analyses of an old workhorse, VM23-81, that was collected in 1966 by Lamont’s R.V. VEMA.
“Relative to most of my colleagues and coworkers in my age group, I am truly a newcomer to the field of paleoceanography. For well more than half of my professional career I was a ‘real geologist’ working on projects that were far removed from the ocean. As Wally mentioned, serendipity played a huge part in my conversion when in the late 1980s he read a proposal submitted by a colleague and myself to use a deep-sea core (DSDP 609) color record to test a method of identifying orbital cycles in Cambrian rocks. Wally rushed into my office telling me that the core’s color record instead revealed the long-sought marine imprint of Greenland’s Dansgaard/Oeschger cycles. I had never heard of Dansgaard/Oeschger cycles, but Wally and other Lamont paleoclimatologists, in particular Rick Fairbanks, managed to convince me that they were much more interesting than Cambrian cycles. By the early 1990s, I had shifted my research from rocks to deep-sea mud.
“In this new field I was surrounded by a baffling array of machines with flashing red lights, toxic chemicals, and coworkers who spoke the languages of chemists, physical oceanographers, and modelers. Fortunately, in North Atlantic deep-sea cores, the first I worked on, I saw something familiar. The assemblages of lithic grains dropped by melting icebergs were much the same as those in sedimentary rocks, the petrology of which was one of my first geological specialties. With only a petrographic microscope as my ‘machine,’ I found fascinating changes in the petrologic composition of the ice-rafted grains. Those changes documented the remarkable extent of Heinrich events in the North Atlantic, revealed a series of rapid, climate-related iceberg discharges that matched Greenland’s Dansgaard/Oeschger cycles, and most recently led to the possibility that changes in solar activity might underlie a series of rapid oscillations punctuating virtually all of the North Atlantic’s Holocene climate record.
“I owe a great debt of gratitude to Bernd Kromer, who first convinced me that the Sun-climate connection was worth pursuing, and encouraged me to undertake what became an arduous two-and-a-half-year-long effort to test that connection. I also must thank my wife, Rusty, curator of Lamont’s core library, for her patience, for her invaluable help on my coring cruises, and for her contributions to many of my papers.”
—GERARD C. BOND, Lamont-Doherty Earth Observatory, Palisades, N.Y.