Preprints
https://doi.org/10.5194/tc-2021-349
https://doi.org/10.5194/tc-2021-349

  18 Nov 2021

18 Nov 2021

Review status: this preprint is currently under review for the journal TC.

Radiative penetration dominates the thermal regime and energetics of a shallow ice-covered lake in an arid climate

Wenfeng Huang1,2, Wen Zhao1, Cheng Zhang1, Matti Leppäranta3, Zhijun Li4, Rui Li1, and Zhanjun Lin2 Wenfeng Huang et al.
  • 1Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region (the Ministry of Education), Chang’an University, Xi’an, China
  • 2State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco Environment and Resources, Chinese Academy of Science, Lanzhou, China
  • 3Institute of Atmospheric and Earth Sciences, University of Helsinki, Helsinki, Finland
  • 4State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China

Abstract. The Central Asia is characterized by cold and arid winter with very little precipitation (snow), strong solar insolation, and dry air. But little is known about the thermal regimes of ice and ice-covered lakes and their response to the distinct meteorology and climate in this region. In a typical large shallow lake, ice/snow processes and under-ice thermodynamics were observed for four winters between 2015 and 2019. Heat budgets at the ice-water interface and within the water column were investigated. Results reveal that persistent bare ice permits 20 %–35 % of incident solar radiation to transmit into the under-ice water, providing background source for under-ice energy flows and causing/maintaining high water temperature (up to 6–8 °C) and high water-to-ice heat flux (annually mean 20–45 W m−2) in mid-winter. Heat balancing indicates that the transmitted radiation and water-to-ice heat flux are the dominators and highly correlated. Both bulk water temperature and its structure respond sensibly to solar transmittance and occasional snow events. Complicated evolution of thermal structure was observed and under-ice convective mixing does not necessarily occur because of the joint governance of strong irradiance, sediment heating and salinity profile. Especially, salt exclusion of freezing changes both the bulk salinity and its structure, which plays a more important role in stability/mixing of the water column in the shallow lake.

Wenfeng Huang et al.

Status: open (until 13 Jan 2022)

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Wenfeng Huang et al.

Wenfeng Huang et al.

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Short summary
Thermal regimes of seasonally ice-covered lakes in arid region like the Central Asia are not well constrained despite its unique climate. We observed annual and seasonal dynamics of thermal stratification and energetics in a shallow arid-region lake. Strong penetrated solar radiation and high water-to-ice heat flux are the predominant components in water heat balance. The under-ice stratification/convection regime is jointly governed by the radiative penetration and salt rejection of freezing.