Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS

Julia de Juan, P. Elosegui, M. Nettles, J. L. Davis, Tine B. Larsen, Andreas P. Ahlstrøm, M. L. Andersen, G. Ekstrom, René Forsberg, G. S. Hamilton, Shfaqat Abbas Khan, K. M. Schild, L. A. Stearns, Lars Stenseng

Research output: Contribution to conferenceConference abstract for conferenceResearch

Abstract

Observations at high spatial and temporal resolution could be key for improving our understanding of the physical processes that govern outlet-glacier flow variations. We collected simultaneous high-rate GPS observations at several locations distributed along and across Helheim Glacier, East Greenland, during the four Arctic summers of 2006-2009, along with other geophysical observations, to study glacial earthquakes and glacier dynamics. GPSderived position estimates of centimeter-level precision reveal the surface expression of glaciological signals, occurring from sub-hourly to daily time-scales and beyond. We find that the flow velocity of Helheim Glacier is modulated by ocean tides in a region including both sides of the grounding line. An admittance analysis of the tidal signal shows an exponential decrease in amplitude with distance from the calving front, along with increasing time delays in both the vertical and horizontal components. Moreover, the along-flow admittance amplitude and time delay estimates are highly time dependent, both with a periodicity of ~15 days, thus suggesting a response to a fortnightly tidal frequency. In addition, we observe transitory increases in the amplitude of the tidally-driven flow response coinciding with glacial earthquakes events, which are associated to large losses of mass at the calving front and step-like increases in flow speed. We will present an analysis of the tidal modulation signals observed at Helheim and discuss how those signals may place new constraints on models for glacier flow variations.
Original languageEnglish
Publication date2009
Publication statusPublished - 2009
Event2009 AGU Fall Meeting - San Fransisco, CA, United States
Duration: 14 Dec 200918 Dec 2009
http://www.agu.org/meetings/fm09/

Conference

Conference2009 AGU Fall Meeting
CountryUnited States
CitySan Fransisco, CA
Period14/12/200918/12/2009
Internet address

Cite this

de Juan, J., Elosegui, P., Nettles, M., Davis, J. L., Larsen, T. B., Ahlstrøm, A. P., ... Stenseng, L. (2009). Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS. Abstract from 2009 AGU Fall Meeting, San Fransisco, CA, United States.
de Juan, Julia ; Elosegui, P. ; Nettles, M. ; Davis, J. L. ; Larsen, Tine B. ; Ahlstrøm, Andreas P. ; Andersen, M. L. ; Ekstrom, G. ; Forsberg, René ; Hamilton, G. S. ; Khan, Shfaqat Abbas ; Schild, K. M. ; Stearns, L. A. ; Stenseng, Lars. / Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS. Abstract from 2009 AGU Fall Meeting, San Fransisco, CA, United States.
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title = "Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS",
abstract = "Observations at high spatial and temporal resolution could be key for improving our understanding of the physical processes that govern outlet-glacier flow variations. We collected simultaneous high-rate GPS observations at several locations distributed along and across Helheim Glacier, East Greenland, during the four Arctic summers of 2006-2009, along with other geophysical observations, to study glacial earthquakes and glacier dynamics. GPSderived position estimates of centimeter-level precision reveal the surface expression of glaciological signals, occurring from sub-hourly to daily time-scales and beyond. We find that the flow velocity of Helheim Glacier is modulated by ocean tides in a region including both sides of the grounding line. An admittance analysis of the tidal signal shows an exponential decrease in amplitude with distance from the calving front, along with increasing time delays in both the vertical and horizontal components. Moreover, the along-flow admittance amplitude and time delay estimates are highly time dependent, both with a periodicity of ~15 days, thus suggesting a response to a fortnightly tidal frequency. In addition, we observe transitory increases in the amplitude of the tidally-driven flow response coinciding with glacial earthquakes events, which are associated to large losses of mass at the calving front and step-like increases in flow speed. We will present an analysis of the tidal modulation signals observed at Helheim and discuss how those signals may place new constraints on models for glacier flow variations.",
author = "{de Juan}, Julia and P. Elosegui and M. Nettles and Davis, {J. L.} and Larsen, {Tine B.} and Ahlstr{\o}m, {Andreas P.} and Andersen, {M. L.} and G. Ekstrom and Ren{\'e} Forsberg and Hamilton, {G. S.} and Khan, {Shfaqat Abbas} and Schild, {K. M.} and Stearns, {L. A.} and Lars Stenseng",
year = "2009",
language = "English",
note = "2009 AGU Fall Meeting, AGU 2009 ; Conference date: 14-12-2009 Through 18-12-2009",
url = "http://www.agu.org/meetings/fm09/",

}

de Juan, J, Elosegui, P, Nettles, M, Davis, JL, Larsen, TB, Ahlstrøm, AP, Andersen, ML, Ekstrom, G, Forsberg, R, Hamilton, GS, Khan, SA, Schild, KM, Stearns, LA & Stenseng, L 2009, 'Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS', 2009 AGU Fall Meeting, San Fransisco, CA, United States, 14/12/2009 - 18/12/2009.

Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS. / de Juan, Julia; Elosegui, P.; Nettles, M.; Davis, J. L.; Larsen, Tine B.; Ahlstrøm, Andreas P.; Andersen, M. L.; Ekstrom, G.; Forsberg, René; Hamilton, G. S.; Khan, Shfaqat Abbas; Schild, K. M.; Stearns, L. A.; Stenseng, Lars.

2009. Abstract from 2009 AGU Fall Meeting, San Fransisco, CA, United States.

Research output: Contribution to conferenceConference abstract for conferenceResearch

TY - ABST

T1 - Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS

AU - de Juan, Julia

AU - Elosegui, P.

AU - Nettles, M.

AU - Davis, J. L.

AU - Larsen, Tine B.

AU - Ahlstrøm, Andreas P.

AU - Andersen, M. L.

AU - Ekstrom, G.

AU - Forsberg, René

AU - Hamilton, G. S.

AU - Khan, Shfaqat Abbas

AU - Schild, K. M.

AU - Stearns, L. A.

AU - Stenseng, Lars

PY - 2009

Y1 - 2009

N2 - Observations at high spatial and temporal resolution could be key for improving our understanding of the physical processes that govern outlet-glacier flow variations. We collected simultaneous high-rate GPS observations at several locations distributed along and across Helheim Glacier, East Greenland, during the four Arctic summers of 2006-2009, along with other geophysical observations, to study glacial earthquakes and glacier dynamics. GPSderived position estimates of centimeter-level precision reveal the surface expression of glaciological signals, occurring from sub-hourly to daily time-scales and beyond. We find that the flow velocity of Helheim Glacier is modulated by ocean tides in a region including both sides of the grounding line. An admittance analysis of the tidal signal shows an exponential decrease in amplitude with distance from the calving front, along with increasing time delays in both the vertical and horizontal components. Moreover, the along-flow admittance amplitude and time delay estimates are highly time dependent, both with a periodicity of ~15 days, thus suggesting a response to a fortnightly tidal frequency. In addition, we observe transitory increases in the amplitude of the tidally-driven flow response coinciding with glacial earthquakes events, which are associated to large losses of mass at the calving front and step-like increases in flow speed. We will present an analysis of the tidal modulation signals observed at Helheim and discuss how those signals may place new constraints on models for glacier flow variations.

AB - Observations at high spatial and temporal resolution could be key for improving our understanding of the physical processes that govern outlet-glacier flow variations. We collected simultaneous high-rate GPS observations at several locations distributed along and across Helheim Glacier, East Greenland, during the four Arctic summers of 2006-2009, along with other geophysical observations, to study glacial earthquakes and glacier dynamics. GPSderived position estimates of centimeter-level precision reveal the surface expression of glaciological signals, occurring from sub-hourly to daily time-scales and beyond. We find that the flow velocity of Helheim Glacier is modulated by ocean tides in a region including both sides of the grounding line. An admittance analysis of the tidal signal shows an exponential decrease in amplitude with distance from the calving front, along with increasing time delays in both the vertical and horizontal components. Moreover, the along-flow admittance amplitude and time delay estimates are highly time dependent, both with a periodicity of ~15 days, thus suggesting a response to a fortnightly tidal frequency. In addition, we observe transitory increases in the amplitude of the tidally-driven flow response coinciding with glacial earthquakes events, which are associated to large losses of mass at the calving front and step-like increases in flow speed. We will present an analysis of the tidal modulation signals observed at Helheim and discuss how those signals may place new constraints on models for glacier flow variations.

M3 - Conference abstract for conference

ER -

de Juan J, Elosegui P, Nettles M, Davis JL, Larsen TB, Ahlstrøm AP et al. Ocean tides modulation of flow at Helheim Glacier, East Greenland, observed using GPS. 2009. Abstract from 2009 AGU Fall Meeting, San Fransisco, CA, United States.