Mathematics – Logic
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmpp62a0323o&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #PP62A-0323
Mathematics
Logic
1620 Climate Dynamics (3309), 1719 Hydrology, 1812 Drought, 3344 Paleoclimatology
Scientific paper
Lake Bosumtwi is a small (8 km-dia.), deep (78 m), hydrologically-closed lake located in the lowland forest zone of southern Ghana, West Africa. The steep-walled meteorite crater basin (10.5 km-dia.) is particularly sensitive to subtle changes in the regional precipitation-evaporation balance, and thus has long been cited as a benchmark paleoenvironmental site for West Africa. In an effort to enhance the value of the Bosumtwi sediments in reconstructing decade to century-scale monsoon variability, we collected a new suite of freeze-cores, and subsequently determined (e.g., with two independent radiometric systems) that the finely laminated sediments represented annual varves (Wheeler et al., AGU Fall Meeting 2002). In light of previous studies, we hypothesized that the ratio of carbon to nitrogen in the lake sediments provides a proxy for changing lake area, and hence regional hydrologic balance and monsoon strength. We confirmed the reliability of this proxy by comparing the sediment based ratio of carbon to nitrogen (C:N) against the age of well-dated dead trees submerged in water depths of 10 to 20m, and then created the first near-annually dated record of West African rainfall extending back eight centuries. The 20th century has been the wettest of the last eight centuries, with the 19th century close behind. Prior to ca. 1800, the Lake Bosumtwi region was generally characterized by drought, with the periods prior to 1300, and 1640 to 1720 AD the driest. This contrasts with comparable records from East Africa, and indicates that much of the Little Ice Age, including some hypothesized periods of reduced solar output, did not result in synchronous enhanced precipitation across North Africa. Instead, it appears that the solar Maunder Minimum resulted in a megadrought in subtropical West Africa coincident with increased rainfall in the Sahel. Thus, the out-of-phase relationship that characterizes interannual variability may extend to longer time scales of variation as well. In addition, anomalously strong Atlantic trade winds and cool SSTs appear to have been associated with the 80-year 17th to 18th century West Africa megadrought.
Arko J.
Beck W.
Cole Joseph
Overpeck Jonathan
Scholz Christina
No associations
LandOfFree
Asynchronous Little Ice Age Megadroughts in Sub-Saharan Africa does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Asynchronous Little Ice Age Megadroughts in Sub-Saharan Africa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Asynchronous Little Ice Age Megadroughts in Sub-Saharan Africa will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1892583