Abstract
AbstractWe have used tide-gauge data from near Helheim Glacier, East Greenland, and GPS data acquired on the glacier to investigate the spectra of tidal forcing and flow response. For both the tide-gauge and GPS time series, we calculated amplitudes and phases for a harmonic expansion using a limited set of harmonic constituents. We find that the semidiurnal constituents of the glacier flow are well modeled using a single admittance and lag with respect to the tide-gauge data. However, diurnal variations in the glacier flow cannot be simply described using this model. We find an additional signal in glacier position, in phase with the S1 solar tide, with some modulations at other frequencies. These non-tidal variations account for a peak-to-peak variation in glacier flow speed at a site close to the terminus of ~0.7 m d-1, compared with a mean flow rate at this location of ~22 m d-1. The speed variations reach their daily maximum value ~6 hours after local noon. We hypothesize that these additional diurnal variations are associated with peaks in lubrication of the glacier bed due to surface melting driven by diurnal solar heating.
Highlights
Glaciers are subject to periodic or quasi-periodic external forcing from a number of sources
Higher-frequency power associated with calving events and, presumably, data noise is present in the power spectral density (PSD)
We compared the spectrum of sea-level time series acquired in Sermilik Fjord near Helheim Glacier with the spectrum of along-flow position time series acquired from a GPS site on the glacier
Summary
Glaciers are subject to periodic or quasi-periodic external forcing from a number of sources. Meier and Post, 1987; Walters and Dunlap, 1987; Vaughan, 1995; Anandakrishnan and Alley, 1997; de Juan and others, 2010; Marsh and others, 2013). Another class of periodic behavior is stick–slip motion modulated by stress changes due to ocean tides (e.g. Bindschadler and others, 2003; Zoet and others, 2012). Glacierflow responses to meltwater forcing have long been known to occur at alpine glaciers (e.g. Iken and Bindschadler, 1986; Bartholomaus and others, 2008), where diurnal and seasonal velocity variations are observed. To our knowledge, diurnal variations in flow due to meltwater variation have not been documented at these marine-terminating glaciers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
