Abstract
AbstractOver a floating glacier ice tongue or an ice shelf, the glacier motion measured by a single, repeat-pass, radar interferogram is difficult to analyze, because the long-term, steady motion of the ice is intermixed with its cyclic, downward motion induced by tidal forcing. Multiple interferograms and a quadruple-difference technique are necessary to separate the tidal signal from the long-term, steady motion of the ice. An example of application of this technique is given here using ERS-1 radar images of Petermann Gletscher, a major outlet glacier of northern Greenland. Tidal displacements are measured with < 5 mm statistical noise. The long-term ice Velocity is measured with a precision of 1 ma−1. The inferred tidal displacements agree well with model predictions from a fixed elastic beam with an elastic damping factor of 0.47 ± 0.01 km3. The hinge line is mapped with a precision of 20-80 m.Combining the interferometric ice velocities with ice thickness data, the glacier ice discharge is calculated at and below the hinge line. At the hinge line, the ice flux is 12.1 ± 1 km3a−1. At the ice front, calf-ice production is only 0.59 km3−1a−1, meaning that 95% of the ice that crosses the grounding line melts before it reaches the calving front. Assuming steady-state conditions, the melt rate of the glacier tongue averages 12 ± 1 m a−1, with peak values exceeding 20 ma−1near the hinge line. This high melt rate cannot be accommodated by surface ablation alone (only about 23 ma−1) and is attributed to pronounced basal melting of the ice tongue. Basal melting, often assumed to be negligible in Greenland, is the dominant process of mass release from the floating section of Petermann Gletscher.
Highlights
Calvin g glaciers play a n essenti a l role in the dyna mics a nd m ass ba lance o f th e Greenl a nd ice sh ee t, and even more so in th e case of th e An ta rctic ice sh eet where ice sheh 'es a nd fl oating g lacier ice to ng ues d evelop ex tensively (H oldsworth, 1977; Dre\\T)' a nd R obin, 1983; Va ug han a nd D oake, 1996 )
At th e iee front, calf-ice production is only 0.59 km 3 a I, meaning th a t 95% of th e ice th a t crosses the gro unding line melts b efore it reaches th e cal ving fro nt
The grounding lin e, wh er e th e ice d ecouples from th e g lacier bed a nd beco m es a fl oat, is impo rta nt to locate precise ly, beca use it p rovid es a referen ce for m oni to ring ch a nges in ice thi c kn ess o r sea leve l indu ced by clim a tic cha nge (Th o m as a nd Bentl ey, 197 8 )
Summary
Calvin g glaciers play a n essenti a l role in the dyna mics a nd m ass ba lance o f th e Greenl a nd ice sh ee t, and even more so in th e case of th e An ta rctic ice sh eet where ice sheh 'es a nd fl oating g lacier ice to ng ues d evelop ex tensively (H oldsworth, 1977; Dre\\T)' a nd R obin , 1983; Va ug han a nd D oake, 1996 ). Of particul a r interes t for studi es of th e sta bili ty of th ese glaciers is th e region a t th e junc ti o n b etween slowe r-m oving inl a nd ice wh ere no tidal displace m en ts occ ur a nd fas ter-m oving ice co mprising th e ice ton g ue or ice sh elf wh er e tid al forcing introdu ces a cycli c, ve rti cal moti on o f the ice surface. G oldstein a nd o th ers ( 1993) d e tec ted th e tid a l m o tion of th e Rutford I ce Stream using a single ERS-l interferog ra m , a nd d ed uced the posi ti o n of th e gro unding line wi thin
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
