Fig. 1
Map of the study area indicating the location of eddy covariance (EC) mast (Universal Transverse Mercator (UTM) zone 27, World Geodetic System (WGS) 84). White contour lines indicate 100 m elevation intervals. Inserted map shows the location of Zackenberg in Northeast Greenland (74.47°N, 20.55°W). The average footprint of the EC system was ca. 200 m long, directed towards southeast, and dominated by Cassiope heath plant community type (Lund et al., 2012).
Fig. 2
Mean July air temperature (T a ) 1996–2010 (a) and maximum active layer depth (Max. ALD) 1997–2010 (b) in Zackenberg, NE Greenland.
Table 1. Mid-summer period surface energy balance and environmental characteristics during the study period 2000–2010
Fig. 3
Environmental characteristics and surface energy dynamics during average year mid-summer period. (a) net radiation (R n ); (b) air temperature (T a ); (c) ratio of sensible heat (H) to R n ; (d) soil volumetric water content (θ v ); (e) ratio of latent heat (LE) to R n ; (f) surface resistance (r s ); (g) ratio of ground heat flux (G) to R n ; (h) Priestley-Taylor α coefficient; (i) Bowen ratio (β); and (j) McNaughton & Jarvis Ω value. Black dots represent means and error bars standard error. Mid-summer period is defined as the period with daily average T a and T 0 above 0°C, positive SW in and R n , and albedo between 10 and 20%. Mean start and end dates during the study period (2000–2010) were 16 June and 1 September, respectively.
Fig. 4
Relationship between within-year variations in Bowen ratio (β) and environmental characteristics during 2003. (a) net radiation (R n ); (b) atmospheric vapour pressure deficit (D a ); and (c) surface saturation vapour pressure deficit (D s ). Observations of β was averaged within bins of 50 W m−2 (R n ) and 100 Pa (D a , D s ), respectively. Black dots represent means and error bars standard deviation.
Fig. 5
Relationship between surface saturation vapour pressure deficit (D s ) and environmental characteristics during 2007. (a) McNaughton & Jarvis Ω value; (b) Priestley-Taylor α coefficient; and (c) surface resistance (r s ). Observations of Ω, α and r s was averaged within D s bins of 100 Pa. Black dots represent means and error bars standard deviation.
Table 2. Average midday, mid-summer meteorological conditions and surface energy partitioning characteristics during 2002 (means±standard deviation)
Fig. 6
Changes in mid-summer surface energy balance partitioning between 2000 and 2010. Lines indicate significant change in data. Error bars for G/R n 2008–2010 indicates uncertainty (St. dev.) in extrapolating ɛ [eq. (4)]. 1-(H/R n +LE/R n ) is a residual term in the energy balance serving as an independent proxy for G. Mid-summer period is defined as the period with daily average T a and T 0 above 0°C, positive SW in and R n , and albedo between 10 and 20%.