From May to September melting and refreezing at the sea ice surface dramatically changes the energy exchange between atmosphere and ocean in the Arctic. Melt ponds play a key role in these changes, because they substantially enhance the absorption of solar radiation due to a considerably lower albedo than that of the surrounding snow/ice.
Goal of the campaign
The primary goal of the aircraft campaign MELTEX-I was to improve the quantitative understanding of the impact of melt ponds on area-average albedo. Measurements aimed to determine pond fraction and broadband as well as spectral surface albedo of pond covered sea ice, and it aimed to collect data that can be used to improve algorithms for the retrieval of melt pond fraction and albedo from satellite measurements (see Roesel et al., 2012, Zege et al., 2015, and Istomina et al., 2015).
The campaign MELTEX-I was a joint project conducted by the Alfred Wegener Institute for Polar and Marine Research (AWI), the Institute for Atmospheric Physics (IPA) at the University of Mainz, and Environment Canada (EC).
The aircraft was equipped with meteorological instrumentation including a spectral albedometer with active horizontal stabilization provided by IPA and with various camera systems and a laser altimeter to obtain information on sea ice surface properties (see Fig. 1). Broadband and spectral surface albedo were derived for clear-sky conditions.
Sea ice conditions
The campaign took place in late spring / early summer, when melt ponds started to form. From 9 May to 8 June 2008, we operated in the Canadian Arctic, mainly over the southern Beaufort Sea with Inuvik as airbase for Polar 5.
Sea ice conditions changed considerably during the campaign from conditions without any melting to a situation with strong melting, especially on fast ice.
Flight over fast ice
On 06 June 2008 a flight was carried out over fast ice in Franklin and Darnley Bay south of the Cape Bathurst coastal polynya in the Amundsen Gulf (Fig. 2). The surface was mainly covered by melt ponds, particle-laden ice, and bare ice (Fig. 3). The total fraction of melt ponds and particle-laden sea ice amounted to 45.0±16.7% with an average clear-sky broadband albedo of 0.14. The average albedo of the remaining bare ice was 0.49 (Fig. 4). The dependence of average clear-sky spectral albedo on the fraction of ponds and particle-laden ice was largest in the visible range and very small for wavelengths larger than 1500 nm (Fig. 5).
- Istomina, L., Heygster, G., Huntemann, M., Schwarz, P., Birnbaum, G., Scharien, R., Polashenski, C., Perovich, D., Zege, E., Malinka, A., Prikhach, A., Katsev, I. 2015. The melt pond fraction and spectral sea ice albedo retrieval from MERIS data – Part 1: Validation against in situ, aerial, and ship cruise data. The Cryosphere 9: 1551-1566. doi:10.5194/tc-9-1551-2015.
- Zege, E., Malinka, A., Katsev, I., Prikhach, A., Heygster, G., Istomina, L., Birnbaum, G., Schwarz, P. 2015. Algorithm to retrieve the melt pond fraction and the spectral albedo of Arctic summer ice from satellite optical data. Remote Sensing of Environment, 163, 153-164. doi:10.1016/j.rse.2015.03.012.
- Rösel, A.; Kaleschke, L., Birnbaum, G. 2012. Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network. The Cryosphere 6: 431-446. doi:10.5194/tc-6-431-2012.