Mass budgets of the Lambert, Mellor and Fisher Glaciers and basal fluxes beneath their flowbands on Amery Ice Shelf

摘要

We used in situ measurements and remote-sensing data sets to evaluate the mass budgets of the Lambert, Mellor and Fisher Glaciers and the basal melting and freezing rates beneath their flowbands on the Amery Ice Shelf. Our findings show the Lambert and Mellor Glaciers upstream of the ANARE Lambert Glacier Basin (LGB) traverse may have positive imbalances of 3.9±2.1 Gt a~(-1) and 2.1 ±2.4 Gt a~(-1), respectively, while the Fisher Glacier is approximately in balance. The upstream region as a whole has a positive imbalance of 5.9±4.9 Gt a~(-1). The three same glaciers downstream of the ANARE LGB traverse line are in negative imbalance, where the whole downstream region has a negative imbalance of -8.5±5.8 Gt a~(-1). Overall the mass budgets of the Lambert, Mellor, and Fisher Glaciers are close to balance, and the collective three-glacier system is also nearly in balance with a mass budget of -2.6±6.5 Gt a~(-1). The significant positive imbalances for the interior basin upstream of the ice-movement stations established in the early 1970s (GL line) reported previously are possibly due to an overestimate of the total accumulation and an underestimate of the ice flux through the GL line.rnThe mean melting rate is -23.0±3.5 m ice a~(-1) near the southern grounding line, which decreases rapidly downstream, and transitions to refreezing at around 300 km from the southern extremity of the Amery Ice Shelf. Freezing rates along the flowbands are around 0.5±0.1 to 1.5±0.2 m ice a~(-1). The percentage of ice lost from the interior by basal melting beneath the flowbands is about 80%±5%. The total basal melting and refreezing beneath the three flowbands is 50.3±7.5 Gt ice a~(-1) and 7.0±1.1 Gt ice a~(-1), respectively. We find a much larger total basal melting and net melting than the results for the whole Amery Ice Shelf derived from previous modeling and oceanographic measurements.