Jökull - 01.01.2013, Side 94

H. Ágústsson et al.
Table1. Location and elevation of the drill sites on Mýrdalsjökull since 2001. – Staðsetning og hæð mælistaða
á Mýrdalsjökli frá 2001.
M0 M1 M2 M3
Longitude [W] 19◦ 3.906’ 19◦ 8.976’ 19◦ 8.796’ 19◦ 15.588’
Latitude [N] 63◦ 36.930’ 63◦ 36.966’ 63◦ 40.620’ 63◦ 38.124’
Elevation [m] 1200 1345 1380 1500
Table 2. Winter layer thickness [m] (not w. eq.) and winter mass balance [mwe], summer balance [mwe] and
annual balance [mwe] at the Mýrdalsjökull drill sites in 2001 and 2007–2012. – Þykkt vetrarlags [m] (ekki
vatnsgildi) og vetrarafkoma [mwe], sumarafkoma [mwe] og ársafkoma [mwe] á mælistöðum á Mýrdalsjökli frá
2001 og 2007–2012.
Site 2001 2007 2008 2009 2010 2011 2012
Spring 12 May 6 May 10 May 9 May 13 May 8 May 17 May
Autumn 29 Aug 9 Sep. 20 Sep. 19 Sep. 15 Sep. 27 Nov.
M0 10.5
Winter M1 11.4 12.7 11.7 11.3 8.4 11.9 11.0
layer M2 8.6 9.1 9.7 9.5 7.6 10.6 9.2
thick. M3 7.6 9.1 8.2 6.3 10.6
M0 5.8
Winter M1 6.8 7.8 6.3 6.0 5.1 6.5 6.6
balance M2 4.5 5.4 5.2 4.7 4.2 5.4 5.2
M3 4.8 4.9 4.4 3.4 5.1
M0 -1.0
Summer M1 -0.9 -1.5 -1.4 -2.1
balance M2 -1.0 -2.7 -1.6 -1.2 -1.4 -3.1
M3 -2.4 -1.1 -0.9
M0 4.8
Annual M1 5.9 4.7 4.6 4.5
balance M2 3.5 2.7 3.5 3.6 4.1 2.1
M3 2.4 3.8 3.4
thereby the thickness of the winter layer. Summer
balance is determined in September from readings of
snow stakes left at the drill sites in May and an as-
sumed mean density of 600–650 kgm−3 of the resid-
ual meltlayer, except for M2 in 2012 which was done
by drilling in late November. The stake positions have
most often been surveyed with DGPS; from which
average surface velocity can be estimated. Difficult
travel conditions on the ice cap during summer and
autumn have affected measurements of summer bal-
ance, which are missing from one or more of the sites
in 2007 and 2010–2012. Moreover, the winter balance
could not be measured at site M3 in May 2011.
No data has previously been published on snow
layer conditions on Mýrdalsjökull by the end of win-
ter. Figure 2 displays basic data on density and tem-
perature in the winter layer in comparison with se-
lected data from Hofsjökull, a 850 km2 ice cap in the
interior highland of Iceland.
Typical spring density profiles at locations M1,
M2 and M3 in 2010 are shown in Figure 2a. Com-
parison of the profiles indicates that greatest densi-
94 JÖKULL No. 63, 2013