ier (84–122 m a−1; Higgins, 1991). At Brikkerne Glacier, velocity was considered to be very slow in 1947, increasing to 150–360 m a−1 in 1963 and 500 m a−1 between 1971 and 1978 (Higgins, 1991). This velocity increase coincided with periods of glacier advance (Higgins, 1991). No records of surging exist for Harder Glacier, but Brikkerne Glacier was identified as surge-type glacier on the basis of variable velocity records (Higgins, 1991; Rignot et al., 2001). Since the early studies (Higgins, 1991; Rignot et al., 2001), little attention has been paid to these glaciers, despite their potential dynamic changes such as surging at Brikkerne Glacier.
Jungersen, Naravana Fjord and Henson Glaciers
Further north from Victoria fjord lie three further outlet glaciers, Jungersen, Naravana Fjord and Henson, which collectively drain 0.7% of northern Greenland (Table 1). Both Jungersen and Henson Glaciers are ~2 km wide (Higgins, 1991) and previously had floating sections (Rignot et al., 2001), although their length has not been reported in the literature. Naravana Fjord, located between these glaciers, is 2.5 km wide and has no floating section. Little is known about terminus changes at these glaciers. Grounding line data (Morlighem et al., 2015) shows they no longer have floating ice tongues (Figure 2A), suggesting their termini have retreated since previous observations (Rignot et al., 2001). Ice velocity data are limited, although Jungersen Glacier was estimated to flow at 350 m a−1 in the 1970s, whereas Henson was barely moving (1.7 m a−1; Higgins, 1991). More recent velocity estimates suggested similar velocities at Jungersen Glacier (395 m a−1), slower flow at Naravana Fjord (59 m a−1), and a much higher estimate for Henson Glacier (286 m a−1: (Rignot et al., 1997).
These glaciers have received little research attention and Rignot et al. (2001) suggested that their significance in terms of ice discharge may have been previously overstated by Koch (1928). This may explain their absence from the majority of northern Greenland research. Nevertheless, they collectively drain a similar area to Tracy Glacier (~3800 km2), and thus represent an important component of the mass budget of the region.
North NE Greenland
At the far north-eastern margin of the GrIS lie several major outlet glaciers (Figure 1) which are Academy, Marie Sophie and Hagen Bræ Glaciers.
Academy and Marie Sophie Glaciers
Academy and Marie Sophie Glaciers collectively drain an area of ~9000 km2 into Independence Fjord (Figure 5C). Academy Glacier has a much wider terminus (8.4 km), compared to Marie Sophie (3.9 km; Table 1), and neither glacier has a floating ice tongue (Figure 2A; Higgins, 1991; Rignot et al., 2001).
Relatively few records of terminus change exist for either glacier. At Marie Sophie, early records showed minimal retreat of 0.06–0.09 km between 1921 and 1956 and sketches by Peary (1892) suggest that Academy Glacier retreated 12 km between 1892 and 1956 (Davies and Krinsley, 1962). More recently, terminus changes showed substantial inter-annual variability between 2000 and 2010 (Murray et al., 2015). Academy Glacier, in particular, advanced (0.59 km) between 2008 and 2009, and subsequently retreated by a similar magnitude (0.49 km) in the following year (2009–2010; Murray et al., 2015). Overall, between 2000 and 2010, both Academy and Marie Sophie Glaciers underwent retreat of 0.9 km and 0.2 km, respectively (Murray et al., 2015).
Early work in the 1970s estimated velocities of 220 m a−1 at Marie Sophie Glacier (Higgins, 1991). This contrasts markedly with more recent values of only 40 m a−1 in 1996 (Rignot et al., 1997) and <100 m a−1 in 2006 (Joughin et al., 2010a). Initial velocity estimates (1970s) at Academy Glacier found values of 256 to 290 m a−1 at the terminus (Higgins, 1991; Rignot et al., 1997). It then maintained a steady velocity of 270 m a−1 from the 1970s to the mid-1990s (Rignot et al., 2001), followed by deceleration between 1996 and 2000/01 (Rignot and Kanagaratnam, 2006). More recently, both Marie Sophie and Academy Glaciers accele