scholarly journals Observing calving-generated ocean waves with coastal broadband seismometers, Jakobshavn Isbræ, Greenland

2012 ◽  
Vol 53 (60) ◽  
pp. 79-84 ◽  
Author(s):  
Jason M. Amundson ◽  
John F. Clinton ◽  
Mark Fahnestock ◽  
Martin Truffer ◽  
Martin P. Lüthi ◽  
...  
Keyword(s):  
Greenland Ice Sheet ◽  
Monitoring Network ◽  
Time Lapse ◽  
Ocean Waves ◽  
Wave Measurements ◽  
Spectral Peaks ◽  
Iceberg Calving ◽  
The Waves ◽  
Coastal Land ◽  
Time Lapse Photography

AbstractWe use time-lapse photography, MODIS satellite imagery, ocean wave measurements and regional broadband seismic data to demonstrate that icebergs that calve from Jakobshavn Isbræ, Greenland, can generate ocean waves that are detectable over 150 km from their source. The waves, which are recorded seismically, have distinct spectral peaks, are not dispersive and persist for several hours. On the basis of these observations, we suggest that calving events at Jakobshavn Isbræ can stimulate seiches, or basin eigenmodes, in both Ilulissat Icefjord and Disko Bay. Our observations furthermore indicate that coastal, land-based seismometers located near calving termini (e.g. as part of the new Greenland Ice Sheet Monitoring Network (GLISN)) can aid investigations into the largely unexplored, oceanographic consequences of iceberg calving.

Calving Signature in Ocean Waves at Helheim Glacier and Sermilik Fjord, East Greenland

2016 ◽  
Vol 46 (10) ◽  
pp. 2925-2941 ◽  
Author(s):  
Irena Vaňková ◽  
David M. Holland
Keyword(s):  
Gravity Waves ◽  
Ocean Waves ◽  
Bottom Pressure ◽  
East Greenland ◽  
Tsunami Waves ◽  
Wave Dynamics ◽  
Resonant Modes ◽  
Spectral Peaks ◽  
Iceberg Calving ◽  
Damped Oscillator

AbstractWhen glaciers calve icebergs, a fraction of the released potential energy is radiated away via gravity waves. The characteristics of such waves, caused by iceberg calving on Helheim Glacier in east Greenland, are investigated. Observations were collected from an array of five high-frequency bottom pressure meters placed along Sermilik Fjord. Calving-generated tsunami waves were identified and used to construct a calving event catalog. Calving events are observed to cluster around high and low semidiurnal tides and around high and prior-to-low semimonthly tides. In the postcalving ocean state, discrete spectral peaks associated with calving events are observed, and they are consistent among all the events. A numerical model is used to compute the resonant modes of the fjord and to simulate calving-generated ocean waves. Damped oscillator boundary forcing with 5- to 10-min periods is found to reproduce well the observed properties of calving waves. These observations and modeling are relevant for better understanding of wave dynamics in glacier fjords.

scholarly journals Seasonal and interannual variations in ice melange and its impact on terminus stability, Jakobshavn Isbræ, Greenland

2015 ◽  
Vol 61 (225) ◽  
pp. 76-88 ◽  
Author(s):  
Ryan Cassotto ◽  
Mark Fahnestock ◽  
Jason M. Amundson ◽  
Martin Truffer ◽  
Ian Joughin
Keyword(s):  
Time Lapse ◽  
Temporal Variations ◽  
Interannual Variations ◽  
Drastic Reduction ◽  
Outlet Glacier ◽  
Secular Changes ◽  
Surface Temperatures ◽  
Iceberg Calving ◽  
Seasonal And Interannual Variations ◽  
Time Lapse Photography

AbstractWe used satellite-derived surface temperatures and time-lapse photography to infer temporal variations in the proglacial ice melange at Jakobshavn Isbræ, a large and rapidly retreating outlet glacier in Greenland. Freezing of the melange-covered fjord surface during winter is indicated by a decrease in fjord surface temperatures and is associated with (1) a decrease in ice melange mobility and (2) a drastic reduction in iceberg production. Vigorous calving resumes in spring, typically abruptly, following the steady up-fjord retreat of the sea-ice/ice-melange margin. An analysis of pixel displacement from time-lapse imagery demonstrates that melange motion increases prior to calving and subsequently decreases following several events. We find that secular changes in ice melange extent, character and persistence can influence iceberg calving, and therefore glacier dynamics over daily-to-monthly timescales, which, if sustained, will influence the mass balance of an ice sheet.

scholarly journals Influence of glacier runoff and near-terminus subglacial hydrology on frontal ablation at a large Greenlandic tidewater glacier

2020 ◽  
pp. 1-10
Author(s):  
Charlie Bunce ◽  
Peter Nienow ◽  
Andrew Sole ◽  
Tom Cowton ◽  
Benjamin Davison
Keyword(s):  
High Frequency ◽  
Greenland Ice Sheet ◽  
Time Lapse ◽  
Temporal Variations ◽  
Hydraulic Efficiency ◽  
Tidewater Glaciers ◽  
Total Mass Loss ◽  
Glacier Runoff ◽  
Iceberg Calving ◽  
Frontal Ablation

Abstract Frontal ablation from tidewater glaciers is a major component of the total mass loss from the Greenland ice sheet. It remains unclear, however, how changes in atmospheric and oceanic temperatures translate into changes in frontal ablation, in part due to sparse observations at sufficiently high spatial and temporal resolution. We present high-frequency time-lapse imagery (photos every 30 min) of iceberg calving and meltwater plumes at Kangiata Nunaata Sermia (KNS), southwest Greenland, during June–October 2017, alongside satellite-derived ice velocities and modelled subglacial discharge. Early in the melt season, we infer a subglacial hydrological network with multiple outlets that would theoretically distribute discharge and enhance undercutting by submarine melt, an inference supported by our observations of terminus-wide calving during this period. During the melt season, we infer hydraulic evolution to a relatively more channelised subglacial drainage configuration, based on meltwater plume visibility indicating focused emergence of subglacial water; these observations coincide with a reduction in terminus-wide calving and transition to an incised planform terminus geometry. We suggest that temporal variations in subglacial discharge and near-terminus subglacial hydraulic efficiency exert considerable influence on calving and frontal ablation at KNS.

scholarly journals An Undular Bore and Gravity Waves Illustrated by Dramatic Time-Lapse Photography

2010 ◽  
Vol 27 (8) ◽  
pp. 1355-1361 ◽  
Author(s):  
Timothy A. Coleman ◽  
Kevin R. Knupp ◽  
Daryl E. Herzmann
Keyword(s):  
Gravity Waves ◽  
Doppler Radar ◽  
Time Lapse ◽  
Radar Data ◽  
Horizontal Wind ◽  
Undular Bore ◽  
Unstable Layer ◽  
Atmospheric Gravity ◽  
The Waves ◽  
Time Lapse Photography

Abstract On 6 May 2007, an intense atmospheric undular bore moved over eastern Iowa. A “Webcam” in Tama, Iowa, captured dramatic images of the effects of the bore and associated gravity waves on cloud features, because its viewing angle was almost normal to the propagation direction of the waves. The time lapse of these images has become a well-known illustration of atmospheric gravity waves. The environment was favorable for bore formation, with a wave-reflecting unstable layer above a low-level stable layer. Surface pressure and wind data are correlated for the waves in the bore, and horizontal wind oscillations are also shown by Doppler radar data. Quantitative analysis of the time-lapse photography shows that the sky brightens in wave troughs because of subsidence and darkens in wave ridges because of ascent.

scholarly journals BEACH FORESHORE RESPONSE TO LONG-PERIOD WAVES

1984 ◽  
Vol 1 (19) ◽  
pp. 132 ◽  
Author(s):  
P.A. Howd ◽  
R.A. Holman
Keyword(s):  
Time Series ◽  
Low Frequency ◽  
Time Lapse ◽  
Mean Square ◽  
Erosion And Deposition ◽  
Frequency Wave ◽  
Long Period ◽  
Typical Time ◽  
The Waves ◽  
Time Lapse Photography

A field experiment has been carried out to test the hypothesis that infragravity and lower frequency waves influence patterns of erosion and deposition on the beach foreshore. The data show coherent fluctuations in the foreshore sediment level which can be related to low frequency wave motions. The fluctuations have heights of up to 6 cm with typical time scales of 8 to 10 minute periods. They can be characterized in two ways: by the progression of the fluctuation up the foreshore slope (landward), and by the decrease in the root-mean-square (RMS) height of the fluctuations as they progress landward. Analysis of runup time series obtained by time-lapse photography concurrent with the sediment level measurements reveals long-period waves of undetermined origin which are positively correlated with the sediment level fluctuations. This strongly suggests that the waves are responsible for forcing the sediment level fluctuations.

The Mechanism of Cell-division

1953 ◽  
Vol s3-94 (28) ◽  
pp. 369-379
Author(s):  
M. M. SWANN
Keyword(s):  
Carbon Monoxide ◽  
Cell Division ◽  
Sea Urchin ◽  
White Light ◽  
Time Lapse ◽  
Psammechinus Miliaris ◽  
Energy Store ◽  
Time Lapse Photography

1. Developing eggs of the sea-urchin Psammechinus miliaris were subjected to carbon monoxide inhibition, which was controlled by changing from green to white light. The behaviour of the eggs was recorded by time-lapse photography. 2. If inhibition is applied before the eggs enter mitosis, their first cleavage is delayed by a time which is roughly equal to the period of the inhibition. 3. If the inhibition is applied when the cells have already entered mitosis, they complete mitosis and cleave with little or no delay, but their second cleavage is delayed by a time which is roughly equal to the period of the inhibition. 4. It is suggested that the necessary energy for the second mitosis and cleavage is being stored up during the first mitosis and cleavage, and that this energy store operates like a reservoir which is continually being filled but siphons out when it is full. Once the energy has siphoned out, it carries mitosis and cleavage through, even though the reservoir is not filling up because of carbon monoxide inhibition.

The generation of waves by wind

1952 ◽  
Vol 215 (1122) ◽  
pp. 299-328 ◽  
Keyword(s):  
Ocean Waves ◽  
Irish Sea ◽  
North Coast ◽  
Empirical Relationships ◽  
The North ◽  
Component Wave ◽  
Wave Trains ◽  
The Irish Sea ◽  
The Waves ◽  
Group Velocities

This paper describes an investigation of the height and length of ocean waves and swell in relation to the strength, extent and duration of the wind in the generating area, and the subsequent travel of the swell through calm and disturbed water. The investigation is based on records of waves made on the north coast of Cornwall, in the Irish Sea and in Lough Neagh. It is a practical continuation of the work of Barber & Ursell (1948), who showed that the waves leaving the generating area behave as a continuous spectrum of component wave trains which travel independently with the group velocities appropriate to their periods. The spectral distribution of energy in the storm area is considered, and the relative amplitudes of the different components are deduced empirically under various wind conditions. The results indicate that the wave characteristics become practically independent of fetch after 200 to 300 miles, and that in the equilibrium condition the steepness of the highest waves is inversely proportional to the square root of the wind speed. Some theoretical foundation can be found for the form of the empirical relationships if it is assumed that the wind acts on each wave component independently, and that the sheltering coefficient used by Jeffreys is proportional to the wave steepness. The results provide a basis for making reasonably accurate predictions of waves and swell from meteorological charts and forecasts.

scholarly journals The determination of glacier speed by time-lapse photography under unfavorable conditions

1992 ◽  
Vol 38 (129) ◽  
pp. 257-265 ◽  
Author(s):  
W.D. Harrison ◽  
K.A. Echelmeyer ◽  
D.M. Cosgrove ◽  
C. F. Raymond
Keyword(s):  
Time Lapse ◽  
Systematic Errors ◽  
Horizontal Motion ◽  
Limited Information ◽  
Glacier Surface ◽  
Alaska Range ◽  
Use Of Time ◽  
West Fork ◽  
Time Lapse Photography

AbstractTwo practical problems in the use of time-lapse photography for the measurement of speed were encountered during the recent surge of West Fork Glacier in the central Alaska Range, Alaska, U.S.A. The first is severe rotational camera instability; we show how natural, unsurveyed features on the valley wall can be used to make the necessary corrections. The second problem is the computation of absolute speed when many different, unsurveyed glacier-surface features are used as targets. We give a method for connecting the data obtained from different targets, and for determining the scale using limited information obtained by surveying. Severe systematic errors can occur unless the angle between the axis of the lens and the direction of horizontal motion is determined.

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