Early climate research at the Preserve:
• Wind Research at Tent Colony
• Heat Budget Research at the Marsh Farm
• Heat Budget Research of Lake Mendota
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By John Kutzbach, published in 2016
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Early Heat Budget Research of Lake Mendota
The “flower pot”–heat budget project on the marsh farm was a test bed for understanding how sunlight, evaporation and air-land exchange of heat combined to explain the workings of crop-covered land. Just a stone’s throw away from the flower pot is a much larger “pot”, a basin of water, Lake Mendota, well-known for adventures of sailing and fishing and swimming, but it is still harboring secrets of how it functions to absorb heat in Summer, evaporate surface water, gradually cool in Fall, and then develop a layer of surface ice during Winter.
It’s unknowns had caught the attention of UW scientists from the universities very first year, 1848, when Prof. Sterling, physics, was charged with recording the dates of freeze and thaw of the lake ice, as well as taking daily meteorological observations from Observatory Hill. In the late 1890s, Prof. Birge, zoologist and limnologist (and UW president in the 1920s – Birge Hall), initiated some of the first scientific studies of Lake Mendota: its flora and fauna, its currents and temperature, and the links between its physics and biology. He published an article on its heat budget in 1915 [Birge, E. A. (1915). The heat budgets of American and European lakes. Trans. Wis. Acad. Sci. , Arts and Letters, 18:166-213.].
This work was later spearheaded by Prof. Art Hasler, first a grad student at the UW in the 1930s and professor from 1941 until retirement in 1978. In the 1930s, limnological research was housed in the “Old Lake Lab” at the base of Park Street (the small brick building used for years by the Hoofers.) The present Laboratory for Limnology, completed in 1963, is located just west of the Old Lake Lab at the start of the Lakeshore Nature Path. For almost 50 years, Prof. Hasler spearheaded extensive limnological research both on Mendota and at Trout Lake in northern Wisconsin; he also gained international renown for his now classic research on the homing behavior of Pacific salmon.
When the Meteorology Department was founded in 1948, Professor Bryson also began lake studies, soon augmented by Prof. Ragotzkie who joined the department in 1959. In those years, a UW floatplane, equipped for science, was moored in University Bay, close to where the Limnos, a boat of the Laboratory for Limnology, is now moored. The plane was the platform for studying lakes throughout the upper Midwest and Canada (picture).
The “flower pot”–heat budget project on the marsh farm was a test bed for understanding how sunlight, evaporation and air-land exchange of heat combined to explain the workings of crop-covered land. Just a stone’s throw away from the flower pot is a much larger “pot”, a basin of water, Lake Mendota, well-known for adventures of sailing and fishing and swimming, but it is still harboring secrets of how it functions to absorb heat in Summer, evaporate surface water, gradually cool in Fall, and then develop a layer of surface ice during Winter.
It’s unknowns had caught the attention of UW scientists from the universities very first year, 1848, when Prof. Sterling, physics, was charged with recording the dates of freeze and thaw of the lake ice, as well as taking daily meteorological observations from Observatory Hill. In the late 1890s, Prof. Birge, zoologist and limnologist (and UW president in the 1920s – Birge Hall), initiated some of the first scientific studies of Lake Mendota: its flora and fauna, its currents and temperature, and the links between its physics and biology. He published an article on its heat budget in 1915 [Birge, E. A. (1915). The heat budgets of American and European lakes. Trans. Wis. Acad. Sci. , Arts and Letters, 18:166-213.].
This work was later spearheaded by Prof. Art Hasler, first a grad student at the UW in the 1930s and professor from 1941 until retirement in 1978. In the 1930s, limnological research was housed in the “Old Lake Lab” at the base of Park Street (the small brick building used for years by the Hoofers.) The present Laboratory for Limnology, completed in 1963, is located just west of the Old Lake Lab at the start of the Lakeshore Nature Path. For almost 50 years, Prof. Hasler spearheaded extensive limnological research both on Mendota and at Trout Lake in northern Wisconsin; he also gained international renown for his now classic research on the homing behavior of Pacific salmon.
When the Meteorology Department was founded in 1948, Professor Bryson also began lake studies, soon augmented by Prof. Ragotzkie who joined the department in 1959. In those years, a UW floatplane, equipped for science, was moored in University Bay, close to where the Limnos, a boat of the Laboratory for Limnology, is now moored. The plane was the platform for studying lakes throughout the upper Midwest and Canada (picture).
University of Wisconsin-Madison plane moored in University Bay. Robert Ragotzkie (Meteorology) and Art Hasler (Limnology). Circa 1955-1960. UW Archives.
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The heat budget of a lake consists of heat gains and loses by the combined processes of radiation, convection and evaporation. Lake Mendota was perfectly situated for study because measurements of these gains and losses were readily available. Solar radiation instruments on the roof of North Hall measured the heat gain. Infrared radiation from the lake, a heat loss—is a function of the lake’s surface temperature moderated by the water vapor in the atmosphere above the lake and clouds—also measured locally. Finally, measurements of temperature and water vapor difference between the lake surface and overlying atmosphere estimated heat gains and losses caused by convection and evaporation.
The broad picture of this heat balance is now clear. The lake starts to gain heat beginning in late winter when sunlight begins to penetrate the ice. The net radiant heating climbs to a maximum around the summer solstice. Thereafter, the effect of the warm surface waters is to lose heat to the atmosphere via evaporation and convection. This loss continues into early winter when the surface cools sufficiently to allow ice to form. Sounding’s of the temperature as a function of depth, illustrated below, reveal that in early spring (March-April) the surface water begins to warm—destroying the isothermal structure of winter when almost the entire lake column below the ice is about 4C (40F)—the temperature at which water has its maximum density. By June the surface temperature is in the range 15-20C (60s F) and the upper10meters have heated by a similar amount. The lake develops a three-layer structure: warm on top, still cold at depth even in summer (10-12C, ~50F) and an intermediate layer called the thermocline (cline = a region of change) separating the warm upper layer from the cold bottom layer. 
The most complete analysis of this budget was completed in 1960 by graduate student John Dutton (now Penn State University) and Reid Bryson [Dutton, J.A., Bryson, R.A. (1962). Heat flux in Lake Mendota. Limnology and Oceanography 7:80-97.] This work was complemented by a detailed study of the heat budget during the period when the lake is covered by ice by graduate student Jon Scott (now Univ. of Albany-SUNY) and Robert Ragotzkie.
[Scott, J. T., Ragotzkie, R.A. (1961). Heat budget of an ice-covered inland lake. Technical Report 6, ONR contract number 1202(7), Univ. of Wisconsin Dept. of Meteorology, Madison, WI]. The flora and fauna of the lake live and move within the lake partly in response to its changing thermal environment. The entire lake goes through a profound change each year when the surface waters cool to 4C, the maximum density, and plummet downward, as is manifested in the graph of late Fall, Winter, and early Spring isothermal temperature sounding of the lake. This convective process leads to the entire lake ‘’overturning’ and re-oxygenating the lower layers which are anoxic (oxygen-depleted) in summer. This overturning profoundly affects the life and chemistry at the lake’s bottom. Mendota has long held the reputation of being the world’s “most studied lake.” |
