Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016-2017

Christian Kienholz, Jason M. Amundson, Roman J. Motyka, Rebecca H. Jackson, John B. Mickett, David A. Sutherland, Jonathan D. Nash, Dylan S. Winters, William P. Dryer, Martin Truffer

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5-4.0 min-1. Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s-1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (~ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min-1) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min-1 for conditions similar to LeConte Bay).

Original languageEnglish (US)
Pages (from-to)195-211
Number of pages17
JournalJournal of Glaciology
Volume65
Issue number250
DOIs
StatePublished - Apr 1 2019

Fingerprint

iceberg
photography
Acoustic Doppler Current Profiler
fjord
spatial resolution
image resolution
eddy
rate

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes

Keywords

  • glaciological instruments and methods
  • ice-ocean interactions
  • icebergs
  • remote sensing

Cite this

Kienholz, C., Amundson, J. M., Motyka, R. J., Jackson, R. H., Mickett, J. B., Sutherland, D. A., ... Truffer, M. (2019). Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016-2017. Journal of Glaciology, 65(250), 195-211. https://doi.org/10.1017/jog.2018.105
Kienholz, Christian ; Amundson, Jason M. ; Motyka, Roman J. ; Jackson, Rebecca H. ; Mickett, John B. ; Sutherland, David A. ; Nash, Jonathan D. ; Winters, Dylan S. ; Dryer, William P. ; Truffer, Martin. / Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016-2017. In: Journal of Glaciology. 2019 ; Vol. 65, No. 250. pp. 195-211.
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Kienholz, C, Amundson, JM, Motyka, RJ, Jackson, RH, Mickett, JB, Sutherland, DA, Nash, JD, Winters, DS, Dryer, WP & Truffer, M 2019, 'Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016-2017', Journal of Glaciology, vol. 65, no. 250, pp. 195-211. https://doi.org/10.1017/jog.2018.105

Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016-2017. / Kienholz, Christian; Amundson, Jason M.; Motyka, Roman J.; Jackson, Rebecca H.; Mickett, John B.; Sutherland, David A.; Nash, Jonathan D.; Winters, Dylan S.; Dryer, William P.; Truffer, Martin.

In: Journal of Glaciology, Vol. 65, No. 250, 01.04.2019, p. 195-211.

Research output: Contribution to journalArticle

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AU - Kienholz, Christian

AU - Amundson, Jason M.

AU - Motyka, Roman J.

AU - Jackson, Rebecca H.

AU - Mickett, John B.

AU - Sutherland, David A.

AU - Nash, Jonathan D.

AU - Winters, Dylan S.

AU - Dryer, William P.

AU - Truffer, Martin

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N2 - We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5-4.0 min-1. Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s-1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (~ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min-1) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min-1 for conditions similar to LeConte Bay).

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KW - ice-ocean interactions

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