n Isbræ (Joughin et al., 2004; Amundson et al., 2010), and on the Antarctic Peninsula (Scambos, 2004). Further complexity in the region arises from surge-dynamics and the literature highlights that several glaciers in this region as potentially surge-type (Mock, 1966; Reeh et al., 1994; Joughin et al., 1996b). We define surges here as the periodic fluctuation between long periods of slow glacier flow (quiescent phase) and short-lived rapid flow, which results in at least an order of magnitude increase (active phase; Meier and Post, 1969; Sharp, 1988). These surge events can be either thermally or hydrologically controlled (Murray et al., 2003) driven by basal temperatures (Fowler et al., 2001) or changes in basal hydrology (Kamb et al., 1985), respectively.
Given that northern Greenland glaciers collectively drain 40% of the GrIS by area (Rignot and Kanagaratnam, 2006) and consist of large catchments, some grounded well below sea-level up to 100 s of km inland (Morlighem et al., 2014), this region has the potential to be a large contributor to future dynamic change, mass loss, and sea level rise.
Here, we review previous research in this region, with a particular focus on recent changes in marine-terminating outlet glaciers and their links to ocean-climate forcing. Our study area is defined by a coastline that is ~2000 km long (Figure 1). This is drained by around 40 marine-terminating outlet glaciers and we focus on a sample of 21 of these glaciers (Figure 1), which represent the primary ice drainage routes where previous work has been undertaken (Higgins, 1991; Rignot et al., 1997, 2001). Many of these glaciers have large catchments overlying deep basal topography, and exhibit high ice velocities (up to 1200 m a−1; Joughin et al., 2010a) that are comparable to fast-flowing outlets elsewhere on the ice sheet (Figure 2). Thus, they have the potential to be large contributors to dynamic mass loss in the future.
Figure 1. Location map of Northern Greenland showing the glaciers reviewed in this paper. The study area has been split into three geographical regions which are Northwest Greenland (3.1), North Greenland (3.2), and Northeast Greenland (3.3). Within North Greenland there are a further three sub-geographical regions, North NW (3.2.1), North Central (3.2.2), and North NE (3.2.3). Colored circles show a first order classification of potential surge-type glaciers across northern Greenland. Red circles show glaciers which are likely to be surge type based on clear surge-cycles having been recorded within the literature. Yellow circles show glaciers at which surging is possible based on glaciers which may have shown surge-characteristics, but either have not been referred to as surge-type or have not undergone a large surge event. Green circles show glaciers at which no evidence of surging has been recorded in the literature. Background image derived from NASA EOSDIS Worldview (16.07.15 and 21.07.15).
Figure 2. (A) Location of large floating ice tongues around the northern Greenland study region based on a review of the literature. Glacier abbreviations relate to Table 1. (B) Bed topography data across Greenland displayed as areas below sea level (<0 m), deep areas in red, shallower bed topography in blue. Both bed topography and floating ice tongue data were derived from the IceBridge BedMachine Greenland, Version 2 dataset in 2015 (Morlighem et al., 2015). (C) Glacier velocities (m a−1) during 2009/10 acquired from the MEaSUREs v2 Greenland velocity dataset (Joughin et al., 2010b) and catchment areas of northern Greenland outlet glaciers derived from hydrological analysis using the Morlighem et al. (2015) bed elevation and ice thickness datasets.
Regional Changes in Glacier Dynamics
Early scientific explorations of northern Greenland by Peary (1892) and the First (1912) and Second (1916–1918) Thule expeditions led by Rasmussen (1912, 1919) sought to improve understanding of the northern margin of the ice sheet. Subsequent studies identified large floating ice tongues, up to 50 km long, on many northern Greenland glacie