Project Info

Freshwater Gas Exchange

Despite the small overall surface area of lakes, reservoirs, streams, and rivers, estimates of carbon dioxide and methane emissions indicate aquatic ecosystems play an important role in carbon balances across multiple scales ranging from the local (ecosystem) scale to the regional and global scales. Lakes are also anticipated to be sentinels of climate change, with the balance between autotrophic growth and respiration in lakes predicted to change with increased anthropogenic activity in their watersheds and with climate change. Studies have been and are being conducted worldwide to assess the role of lakes and reservoirs in regional and global carbon cycles and efforts are underway to estimate metabolic activity in lakes. Essential to these efforts are accurate estimates of gas fluxes at the air-water interface. This research includes an array of field measurements of gas exchange and processes controlling gas exchange across a range of freshwater bodies from small arctic lakes to the large floodplain lakes of the Amazon. These data will be used to validate and improve air-water gas exchange models for freshwater ecosystems (e.g., surface renewal) that are used in biogeochemical models across multiple scales. This multi-scale approach to the measurement and analysis of gas exchange, and the development of gas exchange models over a wide range of latitude, will result in a formulation of the gas transfer coefficient that can be readily applied in ecosystem studies of lakes at any latitude.

Arctic Lakes

Toolik Lake, Alaska (68°N, 149°W, 150 ha)

Toolik Lake in the northern foothills of the Brooks Range is a multi-basin kettle lake with a surface area of 1.5 km2 and a maximum depth of 24 m.

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Temperate Lakes/Rivers

Lake George, New York (43.6°N, 73.6°W)

We are instrumenting a 24 ft. pontoon boat to measure momentum and heat exchange, and air-water concentrations and fluxes of carbon dioxide. A field experiment will be conducted in Lake George (area 11400 ha, 60m depth). The warm water temperatures expected in late summer will lead to increased evaporation and provide a first test that heat loss causes sufficient turbulence near the air-water interface to contribute or drive gas flux.

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Tropical Lakes/Rivers

Lago Grande, Santarem, Para, Brazil (1.5°S, 55.4°oW, >104 ha)

The tropical lake measurements will be made in Lago Grande de Curuai, a large floodplain lake in the Amazon. The lake area varies between roughly 5x10^4 to 20x10^4 ha and the water depth varies between 3-10 m from the high water period to the low water period. The low winds and large heat fluxes suggest that buoyancy driven turbulence will dominate gas exchange in this lake.

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