Abrupt Climate Change

Gadway Sand Barrens, located in the Adirondack Nature Conservancy of New York,
were formed ~13,000 years ago, when a catastrophic flood scoured away the
glacial till on the surface, exposing the Potsdam Sandstone bedrock. The flood
resulted from drainage of glacial Lake Iroquois that released more than
500 km3 of water from Lake Iroquois (Rayburn et al., 2005). The "Flat Rocks"
occur where flood scour was at a maximum. Geologic and glaciological evidence
indicate that the flood may have lasted 2.5 months, and the resulting landforms
and ecosystems still contain unique plant communities, reflecting the
long-term impacts of such abrupt events. Photo provided by T.M. Cronin, USGS.

Abrupt climate change is defined as a large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades, and causes substantial disruptions in human and natural systems. Study of past abrupt changes, preserved in paleoclimate records, provides important evidence on impacts of events that were so rapid and large that recurrence would pose significant risks for society. Examples of such abrupt events include: rapid changes in glaciers and ice sheets that affect sea level, widespread and sustained changes to the hydrologic cycle, shifts in northward flow of warm, salty water in the upper layers of the Atlantic Ocean related to Atlantic Meridional Overturning Circulation, and rapid release of methane trapped in permafrost and on continental margins to the atmosphere.

R&D multidisciplinary research provides a unique opportunity to examine this broad range of topics to inform decision makers on potential impacts and provide ground-truth for climate model scenarios. Paleoclimate researchers at the USGS are reconstructing past responses to abrupt changes that include the Younger Dryas (12.9-11.7 ka), Medieval Climate Anomaly (AD 800-1500) and Little Ice Age (AD 1500-1900). Through examination of terrestrial and marine records from across the North American continent, scientists are improving the understanding of potential rates of change and ecosystem response associate with abrupt events. Ongoing research focuses on:

• reconstruction of temperature and precipitation patterns during the last 10,000 years on local to regional scales across the United States and in adjacent oceans
• evaluation of West Antarctic Ice Sheet response to climate fluctuations of the past 40,000 years
• documentation of magnitudes of past high stands of sea level