Abstract
AbstractWe compare European remote-sensing satellite (ERS) synthetic aperture radar interferograms with artificial interferograms constructed using output of a finite-element ice-shelf flow model to study the dynamics of Filchner-Ronne Ice Shelf (FRIS), Antaretica, near Hemmen Ice Rise (HIR) where the iceberg-calving front intersects Berkner Island. We find that the model must account for rifts, mechanically competent sea ice which fills rifts, and ice softening in coastal boundary layers in order to agree with the ice-deformation pattern implied by observed interferograms. Analysis of the stress field in the model experiment that best matches the observed interferograms suggests that: (1) HIR introduces weakness into the ice shelf through the generation of large-scale rifts, and (2) the melange of sea ice and ice-shelf fragments that fills the rifts stabilizes the shelf front by providing mechanical coupling between the fractured shelf front and the adjacent coast. The rift-filling melange could melt more easily than the surrounding ice shelf and thus could represent a vulnerability of the FRIS to climate warming.
Highlights
As a n initi a l eITort to inte rpret synthe tic a perture rad a r (SAR ) intcrferogra m s of the eastern fl a nk of the ice front of Ro nn e lee Shelf, A ntarctica, desc ribed in a co mpani o n p ap er (Rignot a nd M ac Ayeal, 1998), wc simul ated the rcgim e surroundin g H emmen Ice Ri se (HIR ) (Fig. 1) using a finite-element m odel tha t acco unts fo r g ra\·ita ti o nall y d ri ve n ice-shelf c reep
We are unable to estimate the uncerta inty associated with the icethickness extrapolation, beca use the region of disturbed ice between H emmen Iec Rise (HIR) and BI is least likely to follow the general thickn ess trends of the ice shelf. vVe susp ect, th at it is proba bly much greater tha n the 70 m uncertainty applicable for th e rest of the ice shelf
A unifo rm ice thickness, h = 200 m, was used in stead o f the British Antarctic Survey (BAS) d a ta to elimin a te the indirect innu ence of rifts on n ow due to thickness va ri a ti o ns they may cause in the g ridded a na lysis.Th e fringe lines of the synth eti c interfcrogra m co nstruc ted for ex perime nt I are co ntinuou s throughout th e model domain (Fi gs 6 a nd 7)
Summary
As a n initi a l eITort to inte rpret synthe tic a perture rad a r (SAR ) intcrferogra m s of the eastern fl a nk of the ice front of Ro nn e lee Shelf, A ntarctica ( refe rred to as th e Filchn e r R onne lee Sh elf, o r FRIS), desc ribed in a co mpani o n p ap er (Rignot a nd M ac Ayeal, 1998), wc simul ated the rcgim e surroundin g H emmen Ice Ri se (HIR ) (Fig. 1) using a finite-element m odel tha t acco unts fo r g ra\·ita ti o nall y d ri ve n ice-shelf c reep. 0 adar representing simplified regimes to co mpare with th e real interferogra ms, (2) es tim a te physica l pa ra m e ters, such as the thi ckness of sea iec w hic h fill s rifts, by fittin g modelge nerated interferograms to th eir real co unte rpa rts, a nd (3) furth er va lid a te the perfo rm a nce of the finite-element iceshelf mode l in applicatio ns to th e neighbo rhood of a n iceberg-ca lvin g m a rgin. Th e model must acco unt for mec ha nica ll y compe tent ice mel ange which fill s la rger, older rift. Thi s modificati o n of iceshelf viscos ity m ay be rela ted to strain heating, ice-crys tal alignm ent, c revassing, brin e infiltra ti on a nd tid a l fl exure
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