Features on the Ross Ice Shelf, Antarctica, studied with AVHRR satellite imagery and by modeling

Visible, near infrared and thermal infrared Advanced Very High Resolution Radiometer (AVHRR) imagery at 1.1 km resolution are used to search for changes on the Ross Ice Shelf. Important changes in flow conditions are derived by careful comparison of the imagery with ancillary data. The evidence for ice flow changes derived from AVHRR imagery includes: (1) a large loop of flow stripes observed northwest of Crary Ice Rise interpreted to correspond to an increased activity of ice stream A relative to ice stream B occurring at least 1000 years ago; (2) grounding line retreat on the northeast side of Roosevelt Island over the past 25 years; (3) a lineament 140 km long on the southern part of Roosevelt Island, which could correspond to a stranded shear margin indicating that the ice was much thicker in the past; (4) a disagreement between velocity vectors and AVHRR flow stripes downstream from Steers Head suggesting change in flow conditions in the last 250 years; and (5) a feature 40 km long and 4 km wide close to the grounding line of ice stream C, possibly corresponding to an ice raft torn from the inland ice sheet. These findings are important evidence that confirm the unsteady flow of the West Antarctic ice sheet inferred by other field workers.;Modeling is used to investigate the decay of flow stripes. These features can be traced for several hundred kilometers and yet do not become obscured by snow accumulation. The model predicts that each surface topographic high must overlie a deep root, or keel. The presence of this root accounts for the slow decay time (typically 700 years to decay to 1/e of original size).