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Monsoon History of Vietnam
- L. Stevens
My students and I are currently working on three projects in Vietnam. A brief description of each is listed below.
Winter Monsoon Project
Ba Be Lake (22° 26' N, 105° 37' E) is one of the largest, natural freshwater lakes in Vietnam. It occupies a narrow, N–S trending basin (3 sub-basins) that is approximately 8 km long. Maximum depth is 29 m. The surrounding catchment is steep-sided karst. Ba Be is hydrologically open and is described as polymictic, although mixing usually occurs during early winter. During spring and summer, all three sub-basins are anoxic at depth. The orientation of the lake is parallel to prevailing wind direction, a configuration that results in episodic seiches that bring reduced iron to the surface where it oxidizes. We hypothesize that persistent northerly winds (e.g. strong winter monsoon) would thus enhance upwelling in the north basin, promoting biological productivity through increased nutrient availability. Climatic periods with strong thermal contrasts between land and ocean (e.g. the LIA) should reflect this higher productivity.
Water Sampling Ao Tien (Fairy Pond).
Ba Be is part of a larger cultural and historical site that has recently been declared a National Park.
Nang River near Ba Be.
Nang River near Ba Be.
Historical Heavy Metal Loading Project
Piston coring on Ho Tay. Ho Tay is a diked cut-off meander of the Red River. It is the focal point of Ha Noi and has been for several centuries. We are taking long cores from Ho Tay to examine heavy metal loadings over the last 1000 years. Here we are extruding a meter-long core on a floating restaurant. Everyone likes to help!
Here is my temporary lab. I work with Dr. Vu The Long of the Institute of Archaeology of Vietnam (NCSS), National Center for Social Sciences and Humanities.
Here I am doing basic core description and smear slides.
Coastal Typhoon Project
This is an exploratory project to see if we can reconstruct typhoon strikes along the coast of Vietnam. There are many dune-dammed lakes that serve as freshwater sources for villages. Bioturbation (see picture below) is a problem.
Coring "platform" at Bau Cua. (left)