Time-series analysis of albedo on the Agassiz Ice Cap, Canada

The final glacier analysed was the Agassiz Ice Cap (AIC) shown in Fig. 1.

agassizSS

Figure 1: Study site map for Agassiz Ice Cap. Coordinates refer to UTM (Universal Trans Mercator)
zone 18N. Contour spacing is marked at 500 m and AWS refers to the automatic weather station from which
data was collected. The inset shows shows the location of AIC within the Canadian  Archipelago with coordinates referring to the NSIDC sea ice polar stereographic north system.

The results were broken down into three sections. Firstly, daily albedo measurements provide an overview of the behaviour of albedo throughout the melt season and allow short term fluctuations from the norm to be quantified (Fig. 2).

agassizEvolution

Figure 2: Seasonal evolution of daily albedo on AIC.

Secondly, yearly averages were calculated including maximum and minimums (Fig. 3).

agassizSDMaxMinFinal

Figure 3: Yearly evolution of albedo on AIC.

Finally, regional maps were created highlighting the spatial relationship of albedo fluctuations throughout the time series (Fig. 4).

 

agassizAverageQGISFinal

Figure 4: Regional evolution of albedo on AIC.


Key points from these figures are as follows:

  • Over AIC, αyearly is declining at a rate of 0.0059 ± 0.0013 year-1.
  • The 2012 melt season on AIC witnessed the greatest melt, with albedo values typically < 1σ below the average between June – August.
  • Across AIC, yearly albedo minimums are declining at a rate of 0.0141 ± 0.0019 year-1, nearly three times as rapid as the average.
  • Regionally 76% of the glacier has seen a decline in albedo.
  • Two seasons saw significant deviations (σ) from daily average albedo (αdaily) with mid-June to early-August 2008 measuring 1 σ below, and early-June to mid-August 2012 measuring 2 σ below at peak melt.
  • Daily melt season anomalies, defined as > 1 σ below αdaily, were three times more common in the period 2008 – 2013 than 2001 – 2007.
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