[1] Large lake temperatures are excellent indicators of climate change; however, their usefulness is limited by the paucity of in situ measurements and lack of long-term data records. Thermal infrared satellite imagery has the potential to provide frequent and accurate retrievals of lake surface temperatures spanning several decades on a global scale. Analysis of seventeen years of data from the Along-Track Scanning Radiometer series of sensors and data from the Moderate Resolution Imaging Spectroradiometer shows that six lakes situated in California and Nevada have exhibited average summer nighttime warming trends of 0.11 ± 0.02°C yr À1 (p < 0.002) since 1992. A comparison with air temperature observations suggests that the lake surface temperature is warming approximately twice as fast as the average minimum surface air temperature.

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[1] A unique combination of temporal and spatial measurements provides a description of an extraordinarily large upwelling event in Lake Tahoe, CA-NV. The 4 d event, which engulfed half of the lake's surface and had an amplitude of 500 m, was recorded with in situ and spaceborne instruments. The vertical mixing that ensued, was characterized by a large transfer of heat across the thermocline, resulting in the replacement of the distinct two-layer thermal structure by a diffuse, temperature gradient. Prior to the event, mixing energy due to the cooling flux at the surface was two orders of magnitude larger than the mixing energy associated with the wind. This dominance by cooling yielded the two-layer structure. During the event, wind energy was of similar magnitude to the cooling energy. The large bottom velocities that were produced at the end of the event were sufficient to re-suspend sediment into the water column.

[1] High spatial resolution thermal infrared satellite images acquired 38 minutes apart from Landsat ETM+ and ASTER were used to measure the surface currents and circulation in Lake Tahoe, California-Nevada, USA. Mean currents of 5 -10 cm/s were measured, with maximum currents approaching 35 cm/s. The eastward transport of an upwelling surface jet was clearly apparent, with 15-30 cm/s currents. Three gyres were evident in the vector fields. The satellite image-derived surface currents and circulation patterns are consistent with surface drifter measurements acquired during a different period. These results modify the findings of an earlier study using 1.1 km AVHRR imagery, which concluded there were two counter-rotating gyres in the opposite sense to the two dominant large gyres measured in this study. The high spatial resolution and small time separation allow the surface currents and general circulation in lakes and coastal environments to be accurately quantified using the maximum cross-correlation method. Citation: Steissberg, T. E., S. J. Hook, and S. G. Schladow (2005), Measuring surface currents in lakes with high spatial resolution thermal infrared imagery, Geophys. Res. Lett., 32, L11402,

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