Morphological changes to the terminus of a maritime glacier during advance and retreat phases: Fox Glacier/Te Moeka o Tuawe, New Zealand

Fox Glacier/Te Moeka o Tuawe is a fast-responding maritime glacier that has undergone multiple advance and retreat phases during recent decades. Here we use a combination of repeat photography, Structure from Motion (SfM), and ice discharge measurement, to identify key morphological differences associated with these repeated phase changes, and assess how much of the current terminus is still dynamically active. Increasing surface-debris cover at the margins and topographic shading result in the asymmetry of the retreating terminus, with central portions receding faster than the margins. In 2019, the glacier is shorter than at any time in recorded history, and ice flux is insufficient to sustain the current glacier length, with a further ∼300 m of the glacier terminus region potentially vulnerable to retreat. However, due to the high climate sensitivity of this maritime glacier, even a slight shift towards increasing mass flux could see this trend reverse.