Natural ice is a complex while ubiquitous material to life on Earth, and understanding its physical properties is critical to predictions of 21st century sea level rise and assessments of historical climate change. Current understandings of ice mechanics are generally based on simplifications, due to inherent difficulties in systematically measuring the deformation of ice under controlled low temperature conditions. As the fundamental processes for deformation take place at the nanometre scale, these investigations require the high-precision monitoring of deformation achieved through nanoindentation. Recent developments in cryogenic testing using commercial in situ nanoindentation devices used within a scanning electron microscope (SEM), allow for both the full advantages of small-scale testing together with the ability to test material phases not accessible at ambient temperatures, as for water ice.

In our recent work [1], a methodology has been developed for introducing water ice into the SEM, onto the stage of a commercial nanoindentation device cooled below -30°C, allowing for precise nanomechanical testing of water ice toward cryogenic temperatures under the electron beam (Figure 1). While we determined a hardness and Young’s modulus of ~180 MPa and 4.1 GPa, respectively, within the same order of magnitude as for field studies of ice shelves, a number of ongoing challenges for in situ nanomechanical testing of ice were determined. Ice nanomechanics in the SEM will open up the possibility of addressing systematically a number of open questions in ice mechanics, in particular the role of grain boundaries and chemical impurities on the mechanical response.