In the first part of DOVuFRIS I developed a method that achieves the separation of the melt rate from other dynamics originating from internal motions of an ice shelf that are also present in the received radar signal. This method allowed me to derive melt rate variations as frequent as those due to the semidiurnal (12 hour) tide. I was also able to use these extracted tidal melt rates to gain knowledge about the background oceanic flow beneath the ice shelf, showing that observations of short term variations have a utility when attempting to understand the mean state of a system. Further, I was able to take advantage of the internal tidal motions of an ice shelf to better constrain a mean melt rate estimate at sites where the ice-shelf base is complicated. This is an important result, because complicated ice bases often occur near grounding lines of deep ice shelves, where the rate of melting is highest and where changes in melting have the most profound consequences for ice discharge.
In the second part of DOVuFRIS I was able to identify freezing events that occurred intermittently on the timescale of days to weeks. A new approach was developed to quantify the amount of basal freezing and to infer the nature of the accreted material, which was necessary because melting and freezing in a salty ocean are not symmetric and the properties and therefore radar reflections from ice formed by frozen sea water are different to those from ice formed by snow accumulation. The direct implications of this work is that it will allow the monitoring of the motion of cold waters modified by ice shelf melting, which was previously thought to be impossible using the ApRES technique, and this result can be readily exploited in the planning of upcoming ApRES deployments.
In the final part I worked alongside ocean modellers towards exploiting the ApRES melt rate observations in a way that could improve model validation and inform the design of experiments aimed to improve our understanding of the importance of oceanic variability in ice shelf cavities. We have developed a framework for evaluating the performance of coarsely resolved models and sparse but frequent observations. We have integrated ApRES observations and an ice shelf cavity model to understand the dominant modes of variability at Totten Ice Shelf in East Antarctica. And finally, I have also begun to address the role of mesoscale variability in setting the overall melt rate of an ice shelf.
DOVuFRIS will result in a minimum of six peer-reviewed publications. Two articles have been published, two articles are being revised for resubmission, and two more articles will be submitted shortly. The results have been presented at five international conferences and I have given thirteen invited talks just over the duration of the Fellowship. In addition, there were several activities that went beyond dissemination of the scientific results to the specific audience
of ice-ocean interactions. I convened a session at EGU 2020 drawing the attention of the broader polar science community to the importance of small scale ocean processes in ice-shelf cavities. I also arranged and supervised a summer research experience for two undergraduate students and participated in a Cambridge Science Festival event, exposing the general public and especially children to what it is like to do field research in the polar regions and why it is relevant.
