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Proc Natl Acad Sci U S A. Feb 6, 2007; 104(6): 1751–1753.
Published online Jan 31, 2007. doi:  10.1073/pnas.0609142104
PMCID: PMC1794309

Profile of James P. Kennett

Tinsley H. Davis, Freelance Science Writer

Deep beneath the sea, a precarious truce is born between fire and ice. At low temperatures and high pressures, water molecules form a cage around lighter methane molecules, entrapping this flammable greenhouse gas in a sort of permafrost. With vast reserves of these methane hydrates stored beneath the sea, geologist James P. Kennett has studied their role in past climate change.

In his Inaugural Article in a recent issue of PNAS (1), Kennett, elected to the National Academy of Sciences (NAS) in 2000, described further support for the hypothesis that methane released from the ocean, not from wetlands, triggered rapid rises in temperature many times over the past 60,000 years (2, 3). In looking for ways to document the history of methane emission rates in the Santa Barbara Basin, Kennett and his former graduate student Tessa Hill found a surprising ally: tar. By quantifying the tar deposited in sediment over the last 32,000 years, Kennett, Hill, and colleagues have provided evidence for increases in hydrocarbon seepage associated with periods of rapid deglaciation (1).

Growing Up Down Under

For Kennett, Professor of Earth Sciences at the University of California, Santa Barbara (Santa Barbara, CA), his interest in science started early with a passion for collecting. He was born in 1940 and grew up in Wellington, New Zealand. “I had an inherent interest in natural history. I was practically fanatical. I don't know where it came from. I came from a working-class family,” he says. Kennett's parents allowed him to use an extra room in the house for his own personal museum. “I started collecting,” he says, “anything I could get my hands on, shells, insects, skeletons.” When the family needed the room, his father, a builder, crafted a shed in the backyard for Kennett's collections. Growing up, Kennett spent time at his grandparents' farm in Nelson, a region of New Zealand's South Island, which is geologically diverse. There, he noticed the diversity of rocks and fossils to be found. “I immediately got hooked on geology. I decided at the grand age of 11 that I wanted to be a geologist,” he says.

Back in Wellington, Kennett began hanging around the National Museum and later the New Zealand Geological Survey, where “remarkably sympathetic scientists,” as he describes them, helped Kennett identify all manner of rocks and fossils. One scientist, Norcott Hornibrook, gave Kennett his first samples of foraminifera, a microfossil group that would become critical to Kennett's future research work. Eight years later, another of these scientists, Harold Wellman, would become one of Kennett's university professors. By age 12, Kennett knew the geological timescale by heart. “I was aware of the Earth's ancient and evolutionary paradigm even at that age,” he says.

Kennett recalls that he did most of his learning independently because earth sciences were not taught in schools then, although he did love his biology classes. Kennett entered Victoria University of Wellington (New Zealand) in 1958. During his first year, he worked part-time as the technician in the Geology Department. “Luckily, I was actually hired out of high school to be a lab boy, as it was called in those days!” he says. Kennett worked for Robert Clark, head of the Geology Department. For Kennett, who entered college knowing he wanted to major in geology, “that was a wonderful entree into my academic career,” he says.

Ahead of the Drift

At a time when prevailing theory called for stable landmasses, Kennett and his fellow undergraduates “accepted continental drift as a viable hypothesis,” he says, thanks to John Bradley, whom Kennett recalls as “the New Zealand continental drifter.” As a result, Kennett feels that they were well prepared for the “plate tectonic revolution that was soon to follow,” he says. During Kennett's studies at Victoria University, Henry Pantin of the New Zealand Oceanographic Institute taught a marine geology course, which strongly influenced Kennett's focus. He says, “I thought, ‘There's not much known about the oceans. This is where the future will be. The Earth is 70% oceans.”'

Even before entering a doctoral program, Kennett was well on the way to a career in research. “I published my first papers as an undergraduate and haven't stopped since,” he says (4, 5). He began field work for his Ph.D. in 1961, even though he did not matriculate into the doctoral program at Victoria University until 1963. For his thesis, Kennett wanted to do something different. “It was conventional in those days to do a mapping project,” he says, “[but] I wanted to take an idea and look at it broadly.” He took a time slice of the period between 4 million and 7 million years ago and studied sediments of that age all across New Zealand. Ocean drilling had not started by that time, so he had to look at marine sections tectonically uplifted onto land. He traveled around the country on his motorcycle collecting samples for analysis. To determine relative temperatures, Kennett studied the planktonic microfossils found in the samples.

Kennett's major mentor, Paul Vella, showed him the usefulness of foraminifera, microfossils crucial in learning about Earth's history. “This one group has been absolutely critical,” Kennett says. He estimated water temperature by studying the assemblages of species. “You can distinguish the cold from the warm critters,” he says. Kennett found that significant marine cooling in the late Miocene era corresponded to an inferred drop in sea level recorded in the sediments. “I put two and two together,” he says, and proposed an expansion of the Antarctic ice sheet at that time (6). “Nobody had even thought about the history of the Antarctic ice sheet. It was ignored as part of the climate system,” he says. Scientists in other fields also began to think about the ice sheet in a different way, and geophysicists began to try and figure out its true thickness.

In the Austral summer of 1962–1963, Kennett experienced Antarctica firsthand by participating in a mapping project there unrelated to his thesis. “It was one of those grand life experiences,” he says. He remembers that this time was at the end of continental mapping of virgin territories on Earth, and his team, the Victoria University of Wellington Antarctic Expedition, entered one of the last unexplored areas. This team was the first to explore and map the Darwin Mountains region and even named the geographic features. “It furthered my interest in Antarctica and its ice sheet as a climate engine of the Earth,” he recalls. “Without it, our planet would operate very differently.”

Heading North

Upon finishing his Ph.D. at Victoria University in 1965, Kennett knew he wanted to perform postdoctoral studies overseas. “‘The action's in North America,”' he remembers thinking at the time. Kennett wanted to go to the most innovative laboratory in the then-emerging field of paleoceanography, which uses the ocean to decipher clues about Earth's past. He chose Orville Bandy's laboratory at the University of Southern California (Los Angeles, CA), and he and his wife Diana immigrated to the United States in 1966. In 1968, Kennett published a paper with paleoceanography in the title, which he recalls as one of the first uses of the word (7). Also in 1968, the Deep Sea Drilling Project, led by the United States, began. Over the next 15 years, the project took nearly 600 long cores from beneath the Earth's oceans. “That program has had such a profound effect on our thinking, it's unbelievable. Before drilling we did not have samples of the ocean's history,” he says.

Kennett soon decided that he wanted to teach and accepted a position as an assistant professor in the Department of Geology at Florida State University (Tallahassee, FL). There, he and the late Stan Margolis attempted to “push the envelope on Antarctica's glacial development,” Kennett says. However, the only samples from Antarctica that they had to study were short piston cores. Kennett searched through the university's collection for cores that might have dipped into older sediment. With these “little windows,” he says, “Antarctic ice had been there long before the North American ice of the classic ice-age period” (8, 9).

In 1971–1972, Kennett participated in the first drilling in the South Pacific Ocean. At the time, he was exploring the relationship between plate tectonics and ocean circulation, and thus climate (10). In 1972, Kennett was co-chief scientist on Leg 29 of the Deep Sea Drilling Project, which visited the Subantarctic for the first time. In that work, Kennett and colleagues investigated global environmental responses due to the northward movement of Australia from Antarctica over the last 50 million years and the opening of the oceanic Tasmanian Gateway approximately 33 million years ago. Through the new opening, a circumpolar current developed, and Antarctica became isolated. The resulting isolation of Antarctica affected the development of the ice sheet (11, 12). “The key is this paradigm shift,” he explains of the effect of large-scale continental shifts on ocean circulation changing the heat distribution and thus the climate. This change in thinking led to the modern field of paleoceanography. Continental shifts and resulting current changes affected the long-term climate evolution of the Earth's climate, investigations that Kennett studied with Nick Shackleton. Together Shackleton and Kennett defined major steps in climatic evolution during the last 60 million years (13). The paleoceanographic changes were also found by Kennett to influence strongly the evolutionary pathways of life in the oceans (14).

The Anthrosphere

When Norman Watkins, a close colleague who was also at Florida State University, moved to the University of Rhode Island (Kingston, RI), Kennett followed in 1970 because he wanted to work in a marine science establishment. “My work does not happen in a vacuum. I've had the delight and honor of working with many great graduate students and postdocs,” Kennett says.

He continued along the same research themes in Rhode Island, studying ocean sediment records to understand the history of the planet over the past 65 million years. The work was the forerunner of the new scientific field of Earth System History, which asserts that understanding the planet's history depends on understanding the interrelationships of all of the Earth's parts: hydrosphere, atmosphere, cryosphere, lithosphere, biosphere, and what Kennett calls the anthrosphere, or the human effect.

In 1982, Kennett published the book Marine Geology (15), fulfilling a lifelong ambition to produce such a research text, and in the mid-1980s, he thought, “We really need a new journal.” After lobbying the American Geophysical Union and recruiting papers, Kennett founded the journal Paleoceanography in 1986.

“Tree Rings” in the Ocean

In 1987, Kennett moved to the University of California, Santa Barbara as the Director of the Marine Science Institute. He had two research goals for his tenure there: study the Miocene sequences of the Monterey Formation and use the Santa Barbara Basin for high-resolution studies of climate change. Kennett explains that in studying the basin, he “exploited a local laboratory.” The 600-meter-deep Santa Barbara Basin is a rare site and has such fine resolution that layers can be divided as closely as single years, a phenomenon Kennett calls “the equivalent of tree rings in the ocean.” A high sedimentation rate combined with lack of oxygen in the basin has resulted in few large organisms to disturb the sediment and lots of foraminifera. The area is also highly sensitive to climate change because it is located between two competing currents, the cold California Current from the north and the warmer Southern California Countercurrent from the south.

In the early 1990s, the Ocean Drilling Program, successor to the Deep Sea Drilling Project, drilled a single site in the Santa Barbara Basin. “That was a gold mine of information about the late Quaternary,” Kennett says. The core samples helped him and his colleagues obtain a surprising picture of dynamic climate behavior, including multiple, abrupt warming episodes during the last 70,000 years, which is not long ago in geological terms. These abrupt warmings were first observed in the ice sheets of Greenland and Antarctica (16, 17). Kennett calls it “remarkable climate behavior” and explains that the Earth can move from glacial to interglacial periods in just a few decades, far shorter than the thousands of years assumed.

This finding led Kennett to investigate what forces might cause such abrupt climate change. He studied the Santa Barbara Basin drill core stretching 160,000 years into the past. By looking at oxygen isotopes and foraminifera and using mass spectroscopy, he saw that it looked like a duplicate of the Greenland ice core. The North Pacific appeared to be operating climatically like the North Atlantic region (16). This observation indicated to Kennett that the abrupt changes were also broadly distributed. “It showed the remarkable sensitivity of the Earth's climate system to change,” he says. Kennett explains that little inertia in the climate occurs at certain times. “We have to be careful how we play with our planet,” he cautions. “It can be fickle.”

Implicating Methane

Kennett continued to study processes that might drive these climatic shifts. In 2000, he published evidence of methane release at critical times (2). From air bubbles caught in ice cores (18, 19), rapid warmings have been associated with increased greenhouse gases, like methane, in the atmosphere. Methane is more efficient at trapping heat than another greenhouse gas, carbon dioxide. Methane also has a distinct, carbon isotopic signature, which can be measured on materials such as the calcium carbonate of fossil shells.

When Kennett analyzed fossil shells from the Santa Barbara Basin using mass spectroscopy, large spikes in methane appeared coincident with periods of abrupt climate shift. The American Geophysical Union published a book on what Kennett calls his clathrate gun hypothesis in 2002 (3). Kennett acknowledges that the potential climate-shift role of methane clathrates, the more technical term for hydrate, was and remains controversial. “Methane hydrates have and will continue to play a key role in climate change,” he predicts, “[but] the climate community has largely not accepted the idea of a role.”

Kennett believes that the greatest potential of rapid methane release into the atmosphere is from sediments under the ocean, not in wetlands as others propose. He explains that estimates suggest up to 11,000 gigatons of methane hydrate reserves versus 5 gigatons of reserves of all fossil fuels. “There are arguments about almost everything in this field because it's so young,” he says. But Kennett sees methane studies as outside-the-box thinking, saying, “Eventually, it's likely to be seen as part and parcel of global climate change through time.”

Sticky Samples

In his PNAS Inaugural Article (1), Kennett describes what he calls “a really remarkable, unexpected discovery” made with one of his recent graduate students, Tessa Hill. The work again focused on the Santa Barbara Basin. “This basin keeps turning up surprises,” he says. When Hill was extracting climate records from the samples, she observed an interesting pattern in tar records. Tar accumulates from hydrocarbons that leak out of oil seeps, and Hill found a distinct increase in tar during the deglacial periods. Kennett and Hill quantified the tar deposited over the last 32,000 years. “Instead of being constant, it shows pulses,” Kennett explains. Increases in tar were seen in the two rapid warming intervals at 14,000–16,000 years ago and 10,000–11,000 years ago, when the Earth was switching from glacial to deglacial periods (1).

Kennett explains that the findings could implicate hydrocarbon fields in climate change, with the seeps contributing to the increased methane releases. “We've added another dimension,” he says. Hill and Kennett also examined why the oil pulsed. Oil fields are tied with methane hydrates, and these hydrates destabilize in warmer temperatures, leading to melted plugs and more seepage. In the future, Kennett plans to study similar fields elsewhere to determine whether these pulses are a broader phenomenon.

Kennett recently retired from teaching but has no plans to stop his research or his running. He has run the Boston Marathon three times and even keeps up with daily exercise while traveling. “I explore with my runs,” he says. Kennett is still a collector as well, although his focus now is abalone shells and books about Antarctic exploration. Research has remained in his family. Kennett is delighted to have published with his son Douglas, an Associate Professor in the Department of Anthropology at the University of Oregon (Eugene, OR), most recently on the effect of changing sea level and climate on the emergence of Western civilization in Mesopotamia (20).

figure zpq0060754780001
James P. Kennett
figure zpq0060754780002
Kennett (Left) with son Douglas Kennett, an archaeologist, on San Miguel Island, CA, February 2006.

Footnotes

This is a Profile of a recently elected member of the National Academy of Sciences to accompany the member's Inaugural Article on page 13570 in issue 37 of volume 103.

References

1. Hill TM, Kennett JP, Valentine DL, Yang Z, Reddy CM, Nelson RK, Behl RJ, Robert C, Beaufort L. Proc Natl Acad Sci USA. 2006;103:13570–13574. [PMC free article] [PubMed]
2. Kennett JP, Cannariato KG, Hendy IL, Behl RJ. Science. 2000;288:128–133. [PubMed]
3. Kennett JP, Cannariato KG, Hendy IL, Behl RJ. Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. Washington, DC: Am Geophys Union; 2002.
4. Eade JV, Kennett JP. NZ J Geol Geophys. 1962;5:163–174.
5. Kennett JP. NZ J Geol Geophys. 1962;5:620–665.
6. Kennett JP. NZ J Geol Geophys. 1967;10:1051–1063.
7. Kennett JP. G Geol Ann Del Mus Geologico Bologna. 1968;35:143–156.
8. Margolis SV, Kennett JP. Science. 1970;170:1085–1087. [PubMed]
9. Margolis SV, Kennett JP. Am J Sci. 1971;271:1–36.
10. Kennett JP, Burns RE, Andrews JE, Churkin M, Jr, Davies TA, Dumitrica P, Edwards AR, Galehouse JS, Packham GH, van der Lingen GJ. Nature Phys Sci. 1972;239:51–55.
11. Kennett JP, Houtz RE, Andrews PB, Andrews AR, Gostin VA, Hajos M, Hampton MA, Jenkins PG, Margolis SV, Ovenshine AT, Perch-Nielsen K. Science. 1974;186:144–147. [PubMed]
12. Kennett JP. J Geophys Res. 1977;82:3843–3860.
13. Shackleton NJ, Kennett JP. Paleotemperature History of the Cenozoic and the Initiation of Antarctic Glaciation: Oxygen and Carbon Isotope Analyses in DSDP Sites 277, 279, and 281. Vol XXIX. Washington, DC: US Government Printing Office; 1975. pp. 743–755. Initial Reports of the Deep Sea Drilling Project.
14. Kennett JP. Mar Micropaleontol. 1978;3:301–345.
15. Kennett JP. Marine Geology. Englewood Cliffs, NJ: Prentice Hall; 1982.
16. Dansgaard W, Johnsen SJ, Clausen HB, Dahl-Jensen D, Gundestrup NS, Hammer CU, Hvidberg CS, Steffensen JP, Sveinbjörnsdottir AE, Jouzel J, Bond G. Nature. 1993;364:218–220.
17. Petit JR, Jouzel J, Raynaud D, Barkov NI, Barnola J-M, Basile I, Bender M, Chappellaz J, Davis M, Delaygue G, et al. Nature. 1999;399:429–436.
18. Lorius C, Jouzel J, Raynaud D, Hansen J, Le Treut H. Nature. 1990;347:139–145.
19. Chappellaz J, Barnola JM, Raynaud D, Korotkevich YS, Lorius C. Nature. 1990;345:127–131.
20. Kennett DJ, Kennett JP. J Isl Coastal Archaeol. 2006;1:67–99.

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