Large Lakes Observatory

Paleoclimate: Lake Records and Landscape History

Lakes and landscapes preserve unique records of past climate conditions. LLO researchers are working to develop a broad range of techniques for decoding the signals preserved in lake sediments and landscapes. These approaches are being used to evaluate climate history in East Africa, Central Asia, and North America.

• Bear Lake , North America
• Lake Edward , East Africa
• Issyk-Kul , Central Asia
• Lake Malawi , East Africa
• Lake Nicaragua , Central America
• Lake Qinghai , China
• Lake Superior , North America
• Lake Victoria , East Africa
• Molecular isotopic paleo-studies
• Neotectonics

Bear Lake, Utah-Idaho

Bear Lake is a medium-sized (10 x 30 km) lake that occupies a relatively simple half graben at the boundary between the Colorado Plateau and the Basin and Range. It has many advantages for recording the history of climate change in the western United States: it is a relatively deep marl lake in a glaciated drainage and it has a nearly continuous sedimentary sequence extending more than 250,000 years. A cooperative project among several Universities and the U.S. Geological Survey has been investigating the paleolimnologic and paleoclimate record of the lake. The record turns out to be very complex because groundwater discharge from karst terrain, major hydrological changes related to the changing course of the Bear River, and episodic tectonic activity. Yet this complexity is yielding unexpected insights into the history of the lake and its environment.

Publications:

Colman, S.M., Kaufman, D.S., Bright, J., Heil, C., King, J.W., Dean, W.E., Rosenbaum, J.R., Forester, R.M., Bischoff, J.L., and Perkins, M., 2006, Age models for a Continuous 250-kyr Quaternary lacustrine record from Bear Lake, Utah-Idaho: Quaternary Science Reviews, v. 25, p. 2271-2282, 10.1016/j.quascirev.2005.10.015.

Colman, S. M., 2006, Acoustic stratigraphy of Bear Lake, Utah-Idaho- Late Quaternary sedimentation patterns in a simple half-graben: Sedimentary Geology, v. 185, p. 113-125

Dean, W., Rosenbaum, J., Haskell, B., Kelts, K., Schnurrenberger, D., Valero-Garces, B., Cohen, A., Davis, O., Dinter, D., and Nielson, D., 2002, Progress in global lake drilling holds potential for global change research: EOS, Transactions of the American Geophysical Union, v. 83, p. 85, 90-91.

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Lake Edward, East Africa

Lake Edward is located in the western arm of the East African Rift Valley, situated on the equator between the Democratic Republic of the Congo and Uganda. The lake is in a key location for paleoclimate study, lying at the eastern boundary of the vast, tropical Congo Basin. We completed a reconnaissance survey of Lake Edward in June 1996 with a high-resolution seismic reflection profiling system and collected four cores of 5-8 m length for paleoclimatic study. The cores have undergone extensive paleoclimate analysis, providing valuable new insights into the trends and pulse of African tropical climate.

Publications:

Russell, J. M. and Johnson, T. C., in press. The Water Balance and Stable Isotope Hydrology of Lake Edward, Uganda-Congo.  Journal of Great Lakes Research.

Russell, J. M. and Johnson, T. C., 2005.  Late Holocene climate change in the North Atlantic and Equatorial Africa: Millennial-scale ITCZ migration.  Geophysical Research Letters, v. 32, L17705, doi:10.1029/2005GL023295, 2005.

Russell, J. M., Johnson, T. C., Kelts, K. R., Laerdal, T. and Talbot, M. R., 2003. An 11,000 - year lithostratigraphic and paleohydrologic record from equatorial Africa: Lake Edward, Uganda-Congo. Palaeogeography, Palaeoclimatology, Palaeocecology, v. 193, pp. 25-49.

Russell, J. M., Johnson, T. C., and Talbot, M. R., 2003. A 725 year cycle in the climate of central Africa during the late Holocene. Geology, v. 31, p. 677-680.

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Issyk-Kul, Central Asia

Faculty, staff and graduate students have now completed four expeditions on Issyk-Kul, Kyrgyzstan, in collaboration with Ken Rasmussen, from the Smithsonian Institution, and Vladimir Romanovsky, from the Kyrgyz Institute of Hydroenergetics and Water Problems. Issyk-Kul is the eleventh largest lake in the world by volume (1730 km3) and the fifth deepest (668 m). It is a closed-basin lake at the junction of the Siberian High and the Indian Low, two pressure cells that control atmospheric circulation over central Asia. During the 1997 field expedition, piston cores were collected for paleoclimate studies. The sediment from the cores were analyzed for several paleoclimate proxies, including the stable isotopic and trace element composition of ostracodes. The data show relatively wet conditions around 6000 - 8000 yr before present, followed by dry conditions leading to a closed-basin lake and progressively higher salinities for much of the subsequent 6000 years (Ricketts et al., 2001). Multicores were collected from the lake in 1999 to focus on the most recently deposited sediment and piston cores were collected from the lake in 2000, to extend the record further back in time.

Publications:

Ferronskii, V. I., V. A. Polyakov, V. S. Brezgunov, L. S. Vlasova, Yu. A. Karpychev, A. F. Bobkov, V. V. Romaniovskii, T. C. Johnson, R. D. Ricketts, and K. A. Rasmussen, 2003. Variations in the hydorlogical regime of Kara-Bogaz-Gol Gulf, Lake Issyk-Kul, and the Aral Sea assessed based on data of bottom sediment studies. Water Resources, v. 30, p. 252-259. Translated from Vodnye Resursy, 2003, v. 30, 281-288.

R. D. Ricketts, T. C. Johnson, E. T. Brown, K. A. Rasmussen, and V. V. Romanovsky, 2001. Trace element and stable isotope study of the Holocene paleoclimate of Lake Issyk-Kul. Palaeogeography, Palaeoclimatology, Palaeoecology, 176, pp. 207-227.

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Lake Malawi, East Africa

LLO was funded by the National Science Foundation (NSF) to recover a high-resolution record of past climate change recorded in the varved sediments of northern Lake Malawi. Lake Malawi is the second largest lake in the East African Rift Valley, and is located between 9 and 14 degrees south latitutde. It is about 650 km long and nearly 700 m deep. Piston cores and multicores were recovered in 1997 and 1998 from the north and central basins of the lake. The cores continue to be analyzed for new records of past climate change in the African tropics. The multi-cores contain a 450-year long record of varve thickness and biogenic silica concentrations that show strong evidence for ENSO scale climate variability as well as the impact of the Little Ice Age on this southern African lake. Longer piston cores demonstrate episodes of varve deposition extending back many thousands of years, showing strong links to climate variability in the Northern Hemisphere on a millennial scale.

The paleoclimate records generated by LLO scientists and their collaborators were instrumental in the development of a drilling program on Lake Malawi that was funded by NSF and the International Continental Drilling Program, and carried out in February – March 2005. We drilled two sites – one in the central basin in a water depth of 600 m, to a depth of 385 m below the lake floor, representing roughly the past 1.5 million years of climate change in the African tropics.  The other site was in the north basin, where we triple cored a sediment sequence to a major unconformity that we estimate to be 75,000 years old.  Surprisingly, Lake Malawi, Lake Tanganyika, and Lake Bosumtwi in west Africa all show an arid phase at 75 ka that was more severe than the last glacial maximum (Scholz et al., 2005). Malawi was the first of the large lakes in the East African Rift Valley to be drilled for paleoclimate records.

Publications:

Castañeda, I., Werne, J.P., Johnson, T.C. (2007) Wet/arid phases in the southeast African tropics since the Last Glacial Maximum. Geology. v. 35, no. 9, pp. 823-826.

Brown, E. T., and T. C. Johnson (2005), Coherence between tropical East African and South American records of the Little Ice Age, Geochem. Geophys. Geosyst., 6, Q12005, doi:10.1029/2005GC000959.

Powers, L. A., Johnson, T. C., Werne, J. P., Castaneda, I. S., Hopmans, E. C., Sinninghe Damste, J. S., and Shouten, S., 2005.  Large temperature variability in the southern African tropics since the Lasts Glacial Maximum: Geophysical Research Letters, v. 32, p. L08706, doi:10,1029/2004GL022014, 2005.

Scholz, C.A., Johnson, T.C., King, J.W., Cohen, A.S., Lyons, R.P., Kalindekafe, L., Forman, S.L., McHargue, L.R., and Singer, B.S., 2005, Initial results of scientific drilling on Lake Malawi, East African rift: EOS, Transactions of the American Geohysical Union, v. 86, p. PP13C-03.

Johnson, T. C., Brown, E. T., and McManus, J., 2004. Diatom productivity in northern Lake Malawi during the past 25,000 years: implications for the position of the Intertropical Convergence Zone at millennial and shorter time scales. In: Battarbee, R. and Gasse, F. (ed.) Past Climate Variability Through Europe and Africa. Kluwer Academic Publishers, Dordrecht, 93-116.

Barry, S., Filippi, M., Talbot, M. and Johnson, T., 2002. Sedimentology and geochronology of late Pleistocene and Holocene sediments from Northern Lake Malawi, in: The East African Great Lakes: Limnology, Palaeolimnology and Biodiversity, eds. E. O. Odada and D. O. Olago. Kluwer Academic Publishers, Dordrecht, Netherlands, pp. 369-392.

Gasse, F., Barker, P., Johnson, T., 2002. A 24,000 yr diatom record from the northern basin of Lake Malawi, in: The East African Great Lakes: Limnology, Palaeolimnology and Biodiversity, eds. E. O. Odada and D. O. Olago. Kluwer Academic Publishers, Dordrecht, Netherlands, pp. 393-414.

Johnson, T. C., Brown, E. T., McManus, J., Barry, S., Barker, P., and Gasse, F., 2002. A high-resolution paleoclimate record spanning the past 25,000 years in southern East Africa. Science, 295: 113-114, 131-132.

Johnson, T. C., Barry, S. L., Chan, Y., and Wilkinson, P., 2001. Decadal record of climate variability spanning the last 700 years in the Southern Tropics of East Africa. Geology, v. 29 (1), 83-86.

E.T. Brown, L. Le Callonnec, and C.R. German, 2000. Geochemical cycling of redox-sensitive metals in sediments from Lake Malawi: A diagnostic paleotracer for episodic changes in mixing depth. Geochimica et Cosmochimica Acta, 64, 3515-3523, 2000.

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Lake Nicaragua, Central America

The LLO participated in a reconaissance study of Lake Nicaragua in Central America with scientists from the University of Michigan in Ann Arbor in June 1997. Over 500 km of seismic reflection profiles were obtained using a small airgun, and gravity cores and grab samples were collected at several sites to assess the potential of Lake Nicaraguan sediments as an archive of past climate change in Central America. The sediments throughout the lake contain abundant volcanic ash, reflecting the tectonic setting of the region.

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Lake Qinghai, China, Drilling Project

The sediments of Lake Qinghai, the largest lake in China, are scheduled to be cored in the summer of 2005 in several drill holes, as much as 700 m deep. The drilling operations will be funded by the International Continental Drilling Program and the Chinese Academy of Sciences. Lake Qinghai is a large shallow lake at 3200 m elevation in the northeast corner of the Tibetan Plateau. Its sediments are expected to contain a unique record of climate in this part of Asia, which is affected by the southeast Asian monsoon, the northern hemisphere westerlies, and the Siberian High weather systems. They may also provide insights into the timing of some of the tectonic processes that resulted in the growth of the northeast Tibetan Plateau. Steve Colman and Tom Johnson attended the primary planning meeting for this project in Xining, China, in October, 1993, and Colman serves as one of the primary PIs on the funding proposals. The Large Lakes Observatory plans to participate in the drilling operations and to conduct complementary limnological research on the lake.

Publications:

An, Z., Ai, L., Song, Y., and Colman, S. M., 2006, Lake Qinghai Scientific Drilling Project: Scientific Drilling, v. 2, p. 20-22.

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Lake Superior, North America

The sediments of Lake Superior contain a remarkable varved sequence deposited between 9500 and 11,000 years ago that provides an unusually high-resolution history of meltwater input, as well as catastrophic discharge from Glacial Lake Agassiz through the Superior basin. LLO scientists are deciphering this history using a variety of geochemical and sedimentological analyses, and linking their observations to the North Atlantic region, where Lake Agassiz discharge is thought to have disrupted thermohaline circulation and the climate of northern Europe. The biggest challenge at present is to geochemically distinguish the signals of glacial meltwater from Lake Agassiz water, using a combination of trace element and stable isotope analyses.

Publications:

Breckenridge, A. J., Johnson, T. C., Beske-Diehl, S., Mothersill, J. S., 2004. The timing of regional late glacial events and post-glacial sedimentation rates from Lake Superior.  Quaternary Science Reviews, v. 23, p. 2355-2367.

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Lake Victoria, East Africa

Analyses continue on sediment cores recovered from Lake Victoria as part of the International Decade for the East African Lakes (IDEAL) 1995 and 1996 field seasons. Biogenic silica profiles in the piston cores reflect a strong correlation with oxygen isotope profiles derived from aquatic cellulose. With the paleoclimatological analyses of these sediments cores, results indicate that Lake Victoria, beginning to refill around 14.7 ka after complete desiccation during the last ice age, did not achieve open-basin status until about 11.2 ka, when the Victoria Nile was formed.

Publications:

D. Verschuren, T.C. Johnson, H.J. Kling, D.N. Edgington, P.R. Leavitt, E.T. Brown, M.R. Talbot and R.E. Hecky, 2002. History and timing of human impact on Lake Victoria, East Africa. Proceedings of the Royal Society B: Biological Sciences, 269, 289-294.

Stager, J.C., and Johnson, T.C., 2000. A 12,400 14C year offshore diatom record from east central Lake Victoria, East Africa. Journal of Paleolimnology. 23(4), 373-383.

Johnson, T. C., Kelts, K. and Odada, E. O., 2000. The Holocene history of Lake Victoria, East Africa. Ambio, v. 29, p. 2-11.

Ngobi, G., K. Kelts, T. C. Johnson and P. A. Solheid, 1998. Environmental magnetism of the Late Pleistocene Holocene sequences from Lake Victoria, East Africa. In: Lehman, J. T. (Editor), Environmental Change and Response in East African Lakes, Kluwer Press, Amsterdam, pp. 59 74.

Scholz, C. A., T. C. Johnson, P. Cattaneo, H. Malinga and S. Shana,1998. Initial results of 1995 IDEAL seismic reflection survey of Lake Victoria, Uganda and Tanzania. In: Lehman, J. T. (Editor), Environmental Change and Response in East African Lakes, Kluwer Press, Amsterdam, pp. 47-58.

Johnson, T. C., Y. Chan, K. R. M. Beuning, K. Kelts, G. Ngobi and D. Verschuren, 1998. Biogenic silica profiles in Holocene cores from Lake Victoria: implications for lake level history and initiation of the Victoria Nile. In: Lehman, J. T. (Editor), Environmental Change and Response in East African Lakes. Kluwer Press, Amsterdam, pp. 75-88.

Beuning, K., K. Kelts, E. Ito and T. C. Johnson, 1997. Paleohydrology of Lake Victoria, East Africa, inferred from 18 O/ 16 O ratios in sediment cellulose. Geology, v. 25, p. 1083-1086.

Johnson, T. C., C. A. Scholz, M. R. Talbot, K. Kelts, R. D. Ricketts, G. Ngobi, K. Beuning, I. Ssemmanda and J. McGill, 1996. Late Pleistocene desiccation of Lake Victoria and rapid evolution of cichlid fishes. Science, v. 273, p. 1091-1093.

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Molecular isotopic paleo-studies

New approaches in paleoenvironmental studies utilizing molecular isotopic methods have proven fruitful in many ways. By analyzing the distribution and variability of biomarkers (organic compounds that can be traced to a known biological source) in lake and ocean sediments, we are reconstructing past variations in terrestrial vegetation (e.g., rainforest vs. savannah, C3 vs C4 plant types) and aquatic primary production (e.g. shifts in dominant algal taxa present) in a variety of environments. These vegetation changes can then be related to climate change. Another exciting avenue of molecular isotopic paleoclimate research in which we are involved is the reconstruction of continental paleotemperature and hydrology from lake sediment archives. Specific membrane lipids from crenarchaeota living in the water column have been shown to have a relationship to temperature, and hydrogen isotopes of terrestrial and aquatic biomarkers can be utilized to reconstruct hydrological conditions quantitatively if temperatures are known for a given system. These studies are being carried out in East Africa (Lake Malawi), the USA (Lake Superior and Elk Lake, MN at the headwaters of the Mississippi River), and Mexico (Lago Verde, Los Tuxtlas, Veracruz). Collaborators include J. Sinninghe Damsté, S. Schouten, and E. Hopmans at NIOZ, W. Dean at the USGS, and M. Caballero-Miranda at UNAM.

Publications:

Powers, L.A., J.P. Werne, E.C. Hopmans, J.S. Sinninghe Damsté, S. Schouten (In review '07) Applicability and calibration of the TEX86 paleothermometer in lakes. Submitted to Geochimica et Cosmochimica Acta.

Castañeda, I., Werne, J.P., Johnson, T., and Filley, T. (In review '07) Terrestrial plant biomarkers indicate variability in tropical East African vegetation during the Late Pleistocene and Holocene Submitted to Palaeogeography, Palaeoclimatology, Palaeoecology.

Castañeda, I., Werne, J.P., Johnson, T.C. (2007) Wet/arid phases in the southeast African tropics since the Last Glacial Maximum. Geology. v. 35, no. 9, pp. 823-826.

Powers, L., T.C. Johnson, J.P. Werne, I. Castañeda, E.C. Hopmans, J.S. Sinninghe Damsté, S. Schouten (2005) Large temperature variability in the southern African tropics since the Last Glacial Maximum. Geophysical Research Letters. 32, L08076, doi:10.1029/2004GL022014.

Powers, L., Werne, J.P., Johnson, T.C., Hopmans, E.C., Sinninghe Damste, J.S.S., and Schouten, S., 2004. Crenarchaeotal membrane lipids in lake sediments: a new paleotemperature proxy for continental paleoclimate reconstruction? Geology, v. 32, no. 7, p. 613-616.

Werne, J.P., D.J. Hollander, T.W. Lyons, L.C. Peterson, 2000. Climate-induced variations in productivity and planktonic ecosystem structure from the Younger Dryas to Holocene in the Cariaco Basin, Venezuela Paleoceanography, v. 15, no. 1, pp. 19-29.

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Neotectonics

These studies utilize cosmic ray exposure dating of geomorphological features offset by movement on active faults to estimate slip rates of those faults. Earlier work assumed post-glacial ages for surface features, yielding rapid apparent slip rates and supporting the idea that much of Tibet has been extruded eastward out of India's northward path. This work is showing that many of the surface features are significantly older and that slip rates are correspondingly lower. This suggests, instead, that crustal thickening is the main process by which Asia accommodates India's penetration into it.

Publications:

J.-F Ritz,. D. Bourlès, E.T. Brown, S. Carretier, J. Chéry, B. Enhtuvshin, P. Galsan, R. C. Finkel, T.C. Hanks, K.J. Kendrick, H. Philip, G. Raisbeck, A. Schlupp, D.P. Schwartz, and F. Yiou, 2003. Late Pleistocene to Holocene slip rates for the Gurvan Bulag thrust fault (Gobi-Altay, Mongolia) estimated with 10Be dates. Journal of Geophysical Research, Solid Earth, 108, doi: 10.1029/2001JB000553.

E.T. Brown, R. Bendick, D.L. Bourlès, V. Gaur, P. Molnar, G.M. Raisbeck, and F. Yiou, 2002. Slip rates of the Karakorum Fault, Ladakh, India, determined using cosmic ray exposure dating of debris flows and moraines. Journal of Geophysical Research, Solid Earth, 107, doi: 10.1029/2000JB000100.

E.T. Brown, D.L. Bourlès, B.C. Burchfiel, Deng Qidong, Li Jun, P. Molnar, G.M. Raisbeck, and F. Yiou, 1998. Estimation of slip rates in the southern Tien Shan using cosmic ray exposure dates of abandoned alluvial fans. Geological Society of America Bulletin, 110, 377-386.

E.J. Brook, E.T. Brown, M.D. Kurz, R.P. Ackert, G.M. Raisbeck and F. Yiou, 1995. Constraints on age, erosion and uplift rates of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10 Be and 26 Al. Geology 23, 1063-1066.

J.F. Ritz, E.T. Brown, D.L. Bourlès, H. Philip, A. Schlupp, G.M. Raisbeck, F. Yiou and B. Enktuvshin, 1995. Slip rates along active faults estimated with cosmic-ray exposure dates: Application to the Bogd fault, Gobi-Altaï, Mongolia. Geology 23, 1019-1022.

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