Sequential stagnation of Kamb Ice Stream, West AntarcticaL

Ice-penetrating radar data confirm the presence of two relict northern margins of Kamb Ice Stream (KIS), West Antarctica in an area called the Duckfoot. Between the two relict margins, deep layers are preserved and buried crevasses remain at a constant depth until roughly 1.5 km from the innermost (youngest) margin suggesting that this outer portion of the ice stream stagnated suddenly (<10 years). Stagnation was likely accomplished through changes in basal conditions (i. e., reduced lubrication) beneath this outer portion of the ice stream and resulted in a narrowing of the ice stream trunk by 27% and a reduction in flow speed similar to 200 years prior to complete stagnation. Flowstripe deformation as a result of Duckfoot stagnation provides an estimate of KIS paleo- velocity of 210 m/a after Duckfoot stagnation.