Oceanic and volcanic heat converge in a subglacial channel of the Kamb Ice Stream in West Antarctica

Melting from oceanic heat and basal lubrication from subglacial freshwater are fundamental elements of the West Antarctic Ice Sheet mass balance that are poorly constrained. The ice streams feeding the Ross Ice Shelf grounding line periodically start and stall over decadal to century timescales due to shifts in these forcings. Here, we present in situ hydrographic measurements, noble gas abundances, and helium isotope ratios from a large subglacial channel melted into the base of the stagnant Kamb Ice Stream. These data identify an outflowing plume containing Subglacial Freshwater admixture from upstream volcanic activity and anomalously warm inflowing seawater containing Circumpolar Deep Water from the Ross Sea, with oceanic heat delivery outpacing that from volcanism. Our results directly quantify both variables that affect the mass balance of the Ross Ice Shelf’s sensitive interconnected ice streams and highlight the vulnerability of this region of West Antarctica to increased forcing from a warming climate. Ocean heat flux exceeds that from volcanism by tenfold in a subglacial channel at the base of the Kamb Ice Stream in West Antarctica, which influences its mass balance, according to hydrographic measurements, noble gas abundances, and helium isotope ratios.