Iceberg calving is an efficient ablation process which introduces mechanical instability to
glacier systems and can cause non-linear climatic response. This thesis uses glaciological and
limnological data to examine the relative contributions of calving and melting to mass loss at
glacier termini, and the interplay between glaciological and limnological processes. Calving
dynamics are investigated at two lake-terminating glaciers; Glaciar Leon in Chile and
Fjallsjokull in Iceland. Glaciar Leon, a temperate, grounded outlet of the North Patagonian
Icefield, terminates at an active but stable calving margin in Lago Leones. The calving rate of
880 m a-1 in a mean water depth of 65 m is high for lake-calving glaciers. Detailed survey of
the physical limnology of Lago Leones, important for considering heat transfer to the
subaqueous ice face, revealed thermocline development towards the terminus between
spring and summer. Melting at the waterline along the glacier terminus facilitates calving by
undercutting the subaerial calving cliff, and accounts for around a quarter of mass loss at the
terminus. Waterline melting is also an important rate-controlling process for calving at
Fjallsjokull. Precise quantification of melt rates (subaerial, waterline and subaqueous) at the
termini of calving glaciers is difficult and hazardous, but this study has demonstrated the
value of two techniques: (1) detailed survey of melt notch growth, and (2) use of a radiocontrolled
boat to record water temperatures at the ice-water interface. Continuous
automated monitoring showed that lake-level fluctuations are integral to calving behaviour,
influencing calving event timing and size over diurnal and hourly timescales. Fjallsjokull is
sensitive to climatic forcing whereas Glaciar Leon, which exhibits larger seasonal than
annual fluctuations, is less sensitive. Additional controls on calving at both sites are (1)
buoyancy, (2) longitudinal stretching, and (3) the force balance at the ice-water interface.
Calving operates along a continuum defined by the relative importance of interacting calving
mechanisms, to which the climatic response of calving glaciers is sensitive