Measured horizontal temperature gradients constrain heat transfer mechanisms in Greenland ice

Abstract

Ice in the ablation zone of the Greenland ice sheet is known to contain vertical temperaturegradients that arise from conduction at the boundaries, the addition of strain and latent heat, andadvective heat transport. A three-dimensional array of temperature measurements in a grid of boreholesreveals horizontal ice temperature gradients that challenge the present conceptualization of heattransfer. We measure two distinct types of temperature variability in the horizontal direction, oneimpacting a confined region where ice temperatures span a range of 5°C, and another withtemperatures consistently varying by approximately 2°C across the entire 3-D block. We suggest thefirst demonstrates the localized and limited nature of latent heat input, and the second demonstratesthat vertical heat advection outpaces diffusion. Thesefindings imply that iceflow is highly variable over sub-ice-thickness length scales, which in turn generates contrasts in ice temperature that may impact ice deformation and fracturing.