Surface roughness, sensible heat fluxes (~20–50 W m −2), latent heat fluxes (~2–10 W m −2), topology and scale of turbulence are similar over both glacier surface types during katabatic and synoptically disturbed conditions. We present the first direct comparison of turbulence conditions measured simultaneously over exposed ice and a 0.08 m thick supraglacial debris cover on Suldenferner, a small glacier in the Italian Alps. The future mass balance trajectory of Taku Glacier hinges on dynamics, likely ending the historic dichotomy between these glaciers. These changes initiated terminus retreat, which could increase dramatically if calving begins. Since 2013 negative mass balance and glacier-wide thinning prevailed at Taku Glacier. Divergence in cumulative mass balance arises from differences in glacier hypsometry and local climate. Regional warming trends forced similar statistically significant decreases in surface mass balance after 1989: −0.83 m w.e. The uniform influence of regional climate is demonstrated by strong correlations among annual mass balance and climate data. a −1 at land-terminating Lemon Creek Glacier. a –1, contrasting with retreat and mass loss of −0.60 ± 0.15 m w.e. Tidewater Taku Glacier advanced and gained mass at an average rate of +0.25 ± 0.28 m w.e. Over the 1946–2018 period, the cumulative mass balances diverged. We reanalyzed mass balance records at Taku and Lemon Creek Glaciers to better understand the relative roles of hypsometry, local climate and dynamics as mass balance drivers. We conclude that repeat OPTV borehole logging represents an effective means of measuring distributed vertical strain at millimetre scale, revealing high-resolution variability along the uppermost ~100 m of DIR, Antarctica. Measured strain-rate profiles generally compare closely with output from a 2-D ice-flow model, while the former additionally reveal substantial high-resolution variability. Three coffee-can markers installed at different depths into adjacent boreholes record consistent strain rates and velocities, although averaged over longer depth ranges and subject to greater uncertainty. Both profiles also show substantial local variability.

The resulting profiles decay with depth, from −0.07 a −1 at the surface to ~−0.002 a −1 towards the base in strain and from −1.3 m a −1 at the surface to ~−0.5 m a −1 towards the base in velocity.

We use manual marker tracking and automatic cross correlation between two repeat optical televiewer (OPTV) images of an ~100 m-long borehole at Derwael Ice Rise (DIR), Antarctica, to reconstruct discretised, vertical strain rate and velocity at millimetre resolution. Direct measurements of spatially distributed vertical strain within ice masses are scientifically valuable but challenging to acquire.

Carine crystal crack