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Record #91106:
Bed topography and mass-balance distribution of Columbia Glacier, Alaska, U.S.A., determined from sequential aerial photography / L.A. Rasmussen.
Title: | Bed topography and mass-balance distribution of Columbia Glacier, Alaska, U.S.A., determined from sequential aerial photography / L.A. Rasmussen. |
Author(s): | Rasmussen, L. A. |
Date: | 1988. |
In: | Journal of Glaciology. (1988.), Vol. 34(117) (1988) |
Abstract: | Internally consistent data set of geometry and flow variables for lower part of glacier was derived entirely from vertical air photography. Principle of mass conservation was imposed on data in form of centred finite-difference approximation of continuity equation and applied on 120-node section of square grid covering 15 km long, high-velocity stretch ending at grounded, heavily calving terminus. Photography was obtained 22 times between June 1977 and September 1981. Surface altitudes on dates of flights and displacement vectors between pairs of flights were determined photogrammetrically. Natural features on glacier surface were sufficiently prominent to be followed from date of one flight to next. Altitude points and displacement vectors were irregularly positioned spatially, so interpolation was necessary to obtain values on grid nodes; points had already been subjected to method of optimum interpolation to obtain surface altitudes on grid nodes. Displacement vectors were subjected to constrained-interpolation method to obtain velocity vectors at grid nodes that were consistent, through continuity equation, with other variables. Mass-balance distribution was taken to be separate linear function of altitude for each time interval. Values for bed altitude at 120 nodes and two coefficients of each 21 balance functions were inferred as 162 model parameters in non-linear minimization problem having 4305 observed velocity components as data. |
Notes: | Journal of Glaciology. Vol. 34(117) :208-216 (1988). |
Keywords: | 551.32 -- Glaciology. 551.324 -- Land ice. 551.324.43 -- Land ice, regime and mass balance: Columbia Glacier. 551.331.5 -- Glacial erosion and protection. Sub-glacial topography. E5 -- Glaciology: land ice. (*49) -- Alaska. (*491) -- Alaska, southcentral and southwest. |
SPRI record no.: | 91106 |
LDR 02467naa#a2200000#a#4500 001 SPRI-91106 005 20240329062415.0 007 ta 008 240329s1988####xx#ab#|##|###|0||#0|eng#d 035 ## ‡aSPRI-91106 040 ## ‡aUkCU-P‡beng‡eaacr 100 1# ‡aRasmussen, L. A. 245 10 ‡aBed topography and mass-balance distribution of Columbia Glacier, Alaska, U.S.A., determined from sequential aerial photography /‡cL.A. Rasmussen. 260 ## ‡a[S.l.] :‡b[s.n.],‡c1988. 300 ## ‡ap. 208-216 :‡bdiags., maps. 500 ## ‡aJournal of Glaciology. Vol. 34(117) :208-216 (1988). 520 3# ‡aInternally consistent data set of geometry and flow variables for lower part of glacier was derived entirely from vertical air photography. Principle of mass conservation was imposed on data in form of centred finite-difference approximation of continuity equation and applied on 120-node section of square grid covering 15 km long, high-velocity stretch ending at grounded, heavily calving terminus. Photography was obtained 22 times between June 1977 and September 1981. Surface altitudes on dates of flights and displacement vectors between pairs of flights were determined photogrammetrically. Natural features on glacier surface were sufficiently prominent to be followed from date of one flight to next. Altitude points and displacement vectors were irregularly positioned spatially, so interpolation was necessary to obtain values on grid nodes; points had already been subjected to method of optimum interpolation to obtain surface altitudes on grid nodes. Displacement vectors were subjected to constrained-interpolation method to obtain velocity vectors at grid nodes that were consistent, through continuity equation, with other variables. Mass-balance distribution was taken to be separate linear function of altitude for each time interval. Values for bed altitude at 120 nodes and two coefficients of each 21 balance functions were inferred as 162 model parameters in non-linear minimization problem having 4305 observed velocity components as data. 650 07 ‡a551.32 -- Glaciology.‡2udc 650 07 ‡a551.324 -- Land ice.‡2udc 650 07 ‡a551.324.43 -- Land ice, regime and mass balance: Columbia Glacier.‡2udc 650 07 ‡a551.331.5 -- Glacial erosion and protection. Sub-glacial topography.‡2udc 650 07 ‡aE5 -- Glaciology: land ice.‡2local 651 #7 ‡a(*49) -- Alaska.‡2udc 651 #7 ‡a(*491) -- Alaska, southcentral and southwest.‡2udc 773 0# ‡7nnas ‡tJournal of Glaciology. ‡gVol. 34(117) (1988) ‡wSPRI-20534 917 ## ‡aUnenhanced record from Muscat, imported 2019 948 3# ‡a20240329