INSTAAR Past Global Change Group

Past Global Change Group

The Past Global Change group aims to reconstruct the dynamics of past environmental and climatic variability to understand interactions among components of the global system, including the atmosphere, ocean, land, ice, and biosphere. Integration of a variety of records from a global network of sites, from the polar ice caps to alpine regions in all continents, and from all of the world's oceans, provides the capability to test conceptual and predictive global change models, and to facilitate the differentiation between natural and human-induced change.

Background

The instrumental record that spans the last 100 years is simply too short to capture the full range of climate variability needed to understand natural variability of climate. Longer environmental records are needed. For these we must rely on proxy data from:

the marine sediment record
lake-sediment cores
tree rings
ice cores
corals
and other natural recorders of past environments

In addition to providing a window on the past, these records can be used to identify and understand processes that may affect climate on earth in the coming decades, for example the response of the climate system to changes in the amount of carbon dioxide in the atmosphere.

Human activities are not the only source of greenhouse gases, and paleoenvironmental research done at INSTAAR and elsewhere has shown that the greenhouse blanket has varied in the distant past as well as in this century. Understanding how this system works requires models as well as observations, and INSTAAR is actively engaged in testing and improving numerical models of the components of the global climate system, and how climate interacts with other aspects of the environment.

At INSTAAR, the Past Global Change Group conducts field and laboratory research to produce needed records of past environment, in Colorado and in other parts of North America and the world. Our funding from the National Science Foundation and other sources provides many opportunities for students to participate in research in both the field and the laboratory. Recognizing that climate operates as a system on a global scale, the group's research is not confined to a single discipline or region. The Pole-Equator-Pole (PEP) transect was one of the first international initiatives of the Past Global Changes Program (PAGES), and is well on its way to accomplishing the PAGES (and INSTAAR) objective of producing the panhemispheric array of paleodata needed to understand past climate changes.

Recent Achievements

Digital mapping reveals environmental relationships for past and present glaciers in Alaska. The use of Geographic Information Systems (GIS) enables new avenues for research in glaciology and glacial geology. Spatial analysis makes it possible to examine relationships among mass balance, climate, and terrain for all modern glaciers within one or more mountain ranges. Analysis of past snowlines yields new information on past glacial climates. Online compilations such as the Alaska PaleoGlacier Atlas and Bering Land Bridge Animation foster interdisciplinary collaboration and enhanced visualizations.

Archaeology of the Cryosphere. Global warming is melting glaciers and icefields at an unprecedented rate exposing rare, ancient archeological and paleontological remains. Preliminary research demonstrates that GIS modeling can be used to identify the glaciers and perennial ice patches most probably used by humans. The organic remains locked within these unique and significant environments remain virtually unknown and unexplored by archeologists and other scientists. The apparent rapid acceleration in global warming creates an urgent need to develop scientific methods to locate and preserve these frozen remains as these depositional environments are ephemeral and exposed organic materials soon decompose or are destroyed.

15,000-year continuous record of El Niño climate in the Andes: A lake sediment record from southern Ecuador documents flood events triggered by storms in El Niño years, and shows that the modern El Niño climate pattern did not become established until about 5000 years ago.

First marine record of deglaciation on the coast of Chile: Sediment cores from the Chilean Channels region help document differential timing of deglaciation between the Northern and Southern Hemispheres, and show that deglaciation took place along the Chilean coast about 2000 years before the retreat of continental ice sheets in the Northern Hemisphere.

East Greenland shelf glaciated during the last glacial maximum (LGM): Marine sediment cores and seismic stratigraphy indicate that the Greenland Ice Sheet was more extensive than previously believed, and was a major source of icebergs during deglaciation and other periods of rapid oceanic change (Heinrich Events).

Norse history linked to paleoclimates of Greenland: A synthesis of data from ice cores, marine sediment cores, historical records, and archeological sites show that initial Norse colonization of Greenland (ca. AD 985) took place at the end of a century of relatively mild climate, when sea ice posed no risk to travelers. Ice core isotopic records suggest that the settlers experienced above average temperatures for the first 6 to 12 years after landing, the longest period of "mild" weather for centuries to come. A related multiproxy study documents links among climate, sea-ice extent, and human activity for Greenland and Iceland over the last several centuries

Early Holocene cold event the result of glacial lake drainage: A cold event registered in deep-sea cores throughout the North Atlantic was brought on by rapid influx of cold meltwater from huge glacial lakes that existed south of Hudson Bay at the end of the last glaciation. This study documented the link between abrupt glacier events and large-scale climate.

Heinrich events: Research in eastern Canadian Arctic led the way: Recent reviews clarify the processes and impacts of Heinrich events - pulses of icebergs calved from the Laurentide and other ice sheets that drifted across the North Atlantic in the late Pleistocene and earliest Holocene. Studies by INSTAAR and other researchers of sediments in the Labrador Sea and Baffin Bay have provided evidence for abrupt changes in ice-sheet/ocean interactions.

Great Basin Pleistocene insect fauna show links with Pacific Northwest-style climate: Llate Pleistocene beetle faunas from packrat middens in Nevada are comprised of species mainly found today in the Pacific Northwest region, from the Alaskan Panhandle to northern California. This research shows that late Wisconsin climate in the Great Basin was substantially cooler and wetter than it is today.

Beetle evidence for a Younger Dryas oscillation in Beringia: The past climate of Siberia, Alaska, and the Yukon was clarified through use of the new Mutual Climatic Range (MCR) method. Results show a dramatic rise in summer temperatures just prior to 11,000 14C yr B.P., followed by rapid cooling (on the order of 7°C mean July temperature). This phenomenon has been documented in pollen profiles, but the temperature changes have never before been quantified.

Patagonian lakes yield sediment records spanning the late Pleistocene: Following initial seismic, neolimnologic and coring surveys of three closed-basin lakes in Argentina at latitudes 31, 41, and 49°S, present research focuses on the southernmost, 76m deep lake, Lago Cardiel. Several over 11m long Kuhlenberg cores recovered in 1999 from a specially built boat, are presently being dated and analyzed for their sedimentologic and geochemical characteristics as well as for pollen, diatoms, ostracodes and stable isotopes. Preliminary results show major and rapid lake level fluctuations during the past 20,000 years, including short-term desiccation intervals in pre-fullglacial and late glacial times This record will provide an outstanding history of high southern latitude climate change, reflecting changes in circum-Antarctic sea-ice and the southern westerly stormtracks.

Colorado Front Range Drought: The 2002 drought presented new opportunities for applying tree-ring reconstructions of streamflow to water resource management. Partnerships with major Front Range water management agencies have been developed to explore ways the extended hydrologic records can be used by managers. Reconstructions of gages of interest to Denver Water and the Northern Colorado Water Conservation District for the Upper Colorado and S. Platte River basins are currently under development.
Dendroclimatic reconstructions of streamflow for South Platte basin streams and drought for eastern Colorado reveal a period of drought unequaled in the 20th century. New reconstruction techniques have been applied to define variance in the reconstructions, making these data more useful to water resource managers.

Modern carbon sinks: Ten years of isotope measurements of atmospheric carbon dioxide in cooperation with NOAA reveal large carbon sinks in the terrestrial biosphere of the Northern Hemisphere, as well as in tropical forests.

Ice core evidence of rapid climate change: Stable isotopes in ice cores document large, rapid climate warmings in the North Atlantic region. Recent evidence from Antarctic ice cores suggests that rapid climate communication between the hemispheres is possible. Also, evidence of ENSO oscillations persist throughout the Holocene in these ice cores.

Sea Ice in the Climate System: Lessons from the North Atlantic Arctic. The human consequences of more extensive sea-ice during the Little Ice Age are well documented for Iceland, and are paralleled by other impacts that reverberate through the global climate system. The role of sea ice in the climate system was the topic of an international meeting held in Iceland. The probable impact of reduced sea ice during the warm early Holocene was estimated, showing most impacts are concentrated in the North Atlantic (not the North Pacific) despite symmetric forcing, and in the winter months.

Kostenki: Earliest modern humans in Eastern Europe. This interdisciplinary project is investigating the oldest known traces of modern humans in Eastern Europe at archaeological sites located 450 km south of Moscow on the Don River. During 2001-2002, the lowest levels of these sites yielded early evidence of complex technology and art, reflecting behavioral changes that probably played a critical role in modern human dispersals and the related disappearance of the European Neanderthals. A major focus of the Kostenki project is stratigraphy, geochronology, and site formation processes.

See also:

For a snapshot of past activities, view the Past Global Change Group Description in the 1998 INSTAAR Annual Report (PDF file; 2076 KB).
Environmental Change in High-Latitude Oceans and Lakes (ECHOL)
Laboratory for Radiocarbon Preparation and Research
Stable Isotope Laboratory
Quaternary GIS Laboratory
Smith, L. M., and Licht, K.J., compilers, 2000, Radiocarbon Date List IX: Antarctica, Arctic Ocean, and the Northern North Atlantic: INSTAAR Occasional Paper No. 54, 138 pp.