The optical measurement program was designed to investigate the ice-albedo 
feedback. In particular we wanted to determine the distribution of the solar 
energy incident on the ice cover; how much is reflected from the ice, how much 
is absorbed in the ice, and how much is transmitted to the ocean. 

 Optical measurements consisted of
     (1) albedo both spectral (SPECALB) and total (TOTALB) values ,
     (2) transmittance spectral irradiance through the ice and in the upper 
         few meters of the ocean (TRANS)
     (3) in-ice irradiance profiles (IN_ICE)
     (4) incident ultraviolet irradiance (UVINC). 

We used a variety of field-portable spectrophotometers and shortwave radiometers 
to make these measurements. The spectrophotometers all have very rapid response 
times and typically make a full suite of spectral measurements in less than a second. 
Calibration and intercomparison of these instruments was performed routinely while in 
the field. Irradiance measurements in the Arctic are prone to inaccuracies resulting 
from the large solar zenith angles found at high latitudes. To alleviate this problem 
we used integrating sphere cosine collectors on sunny days. For albedo measurements, 
the detectors were mounted on a 1.5-m-long arm to minimize shadowing of the surface. 
A specially designed, two-detector, enhanced sensitivity spectroradiometer (ASD Ice-1) 
was used to measure light transmitted through the ice cover. With one detector remaining 
on the surface to monitor incident irradiance, the other detector was mounted on an 
articulated arm, lowered through a 15 cm diameter hole in the ice, then swung up and 
placed on the ice bottom 1.5 m away from the hole.