Surface temperature
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Surface temperature |
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| A significant component of the summer mass balance is
the temperature distribution in leads versus the ponded ice. An important
question is how much of the solar and longwave radiation absorbed by the
water remains in the surface layers and is available for lateral melting.
To relate detailed surface-based observations in a few leads near
the ship to the local and intermediate spatial scales, periodic helicopter-based observations were carried out in conjunction with the photographic
surveys from mid-June through late August, including spatial transects of
up to 100 km. A Heimann Kt-19 infrared radiometer recording in a
wavelength band of 8-14 microns was mounted looking directly downward below
the helicopter. Its field of view was approximately 2 degrees, providing a
spatial resolution at the surface of 1/30 of the altitude or
about 75 m at 1800 ft. Data were sampled at 1 Hz, providing an
overlap of about 20% of the field of view at this elevation. This was
sufficient to resolve the major leads and polynyas.
Representative results seen in the accompanying figures show the contrast between the ice and the cold water that was exposed upon lead opening near –1.8oC (30 June) followed by the transition to the opposite situation (25 July) where the lead surface was nearly 2oC warmer than the ice due to radiation absorption in the water in conjunction with weak vertical mixing. The relative radiometric accuracy of the measurements is approximately ± 1oC. The data files are designated as KT19mmdd.csv, where mm denotes the month and dd the day. Each file contains observed infrared brightness temperature in degrees Celsius versus the local time in decimal hours
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30 June 1998: leads are colder than ice. |
25 July 1998: leads warmer than ice due to solar heating. |
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