Simulation of the cold climate event 8200 years ago by meltwater outburst from Lake Agassiz

The cold climate anomaly about 8200 years ago is investigated with CLIMBER-2, a coupled atmosphere-ocean-biosphere model of intermediate complexity. This climate model simulates a cooling of about 3.6 K over the North Atlantic induced by a meltwater pulse from Lake Agassiz routed through the Hudson strait. The meltwater pulse is assumed to have a volume of 1.6 x 10^14 m^3 and a period of discharge of 2 years on the basis of glaciological modeling of the decay of the Laurentide Ice Sheet ( LIS). We present a possible mechanism which can explain the centennial duration of the 8.2 ka cold event. The mechanism is related to the existence of an additional equilibrium climate state with reduced North Atlantic Deep Water (NADW) formation and a southward shift of the NADW formation area. Hints at the additional climate state were obtained from the largely varying duration of the pulse-induced cold episode in response to overlaid random freshwater fluctuations in Monte Carlo simulations. The model equilibrium state was attained by releasing a weak multicentury freshwater flux through the St. Lawrence pathway completed by the meltwater pulse. The existence of such a climate mode appears essential for reproducing climate anomalies in close agreement with paleoclimatic reconstructions of the 8.2 ka event. The results furthermore suggest that the temporal evolution of the cold event was partly a matter of chance.

Letter book : manuscript, 1757-1759

Contains chiefly correspondence with Secretary of State William Pitt, including a letter, dated 22 Sept. 1759, describing the fall of Québec and the death of Wolfe.

Adirondack Mountains Region, New York, 1876 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Map of the New York wilderness : to accompany Wallace's Descriptive guide to the Adirondacks, by W. W. Ely. It was published by G. W. & C. B. Colton & Co. in 1876. Scale [1:253,440]. Covers the Adirondack Mountains Region including portions of St. Lawrence, Franklin, Clinton, Lewis, Herkimer, Hamilton, Essex, Oneida, Warren, and Saratoga Counties. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM) Zone 18N NAD83 projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as roads, railroads, hotels, and township and county boundaries and more. Relief is shown by hachures and spot heights. Includes inset: [Northeastern states]. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.

Adirondack Mountains Region, New York, 1883 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Map of the Adirondack wilderness, compiled by S.R. Stoddard. 4th rev. ed. It was published by S.R. Stoddard in 1883. Scale [ca. 1:255,000]. Covers the Adirondack Mountains Region, New York, including portions of St. Lawrence, Franklin, Clinton, Lewis, Herkimer, Hamilton, Essex, Warren, and Saratoga Counties. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator (UTM) Zone 18N NAD83 projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as natural features, drainage, railroads, important roads, ordinary roads, carries and trails, and township and county boundaries, and more. "Distances are given in Figures on Roads and Trails. Air-Line Distances from Mount Marcy are indicated by Circles, 10 miles apart." Relief is shown by hachures and spot heights. This layer is part of a selection of digitally scanned and georeferenced historic maps from The Harvard Map Collection as part of the Imaging the Urban Environment project. Maps selected for this project represent major urban areas and cities of the world, at various time periods. These maps typically portray both natural and manmade features at a large scale. The selection represents a range of regions, originators, ground condition dates, scales, and purposes.