Ice Shelf Water Structure Beneath the Larsen C Ice Shelf in Antarctica

Abstract

Understanding ice shelf water (ISW) structure is crucial for studying the basal melting of ice shelves. In this study, we performed large-eddy simulation experiments to assess ISW structure and basal melt patterns under different current velocity scenarios observed in the Larsen C ice shelf, Antarctica. The LES results revealed that the thickness of ISW is primarily determined by the meridional velocity (perpendicular to the grounding line), while the zonal velocity influences the potential temperature and salinity of ISW. We found that a key parameter determining the basal melt rate was northward meltwater advection which originates from variances in meltwater generation. This advection, in turn, leads to the tilted isopycnals and the potential for thermohaline interleaving in a diffusive convection regime. The different slopes of isopycnals induce distinct heat fluxes, resulting in different basal melt rates far from and near the grounding line (similar to 0.44 and 1.59 m yr-1, respectively). The loss of ice mass from the Antarctic ice sheet is accelerating, posing a threat to human lives through global sea level rise. Understanding ice shelf water (ISW), which refers to seawater below freezing temperature, is crucial as it directly or indirectly influences basal ice melting. However, direct observations are extremely challenging, leaving this understanding unclear. To tackle this issue, we utilized a numerical model to gain insight into the fundamental characteristics of ISW. We demonstrated that the direction and magnitude of ocean currents beneath the ice shelf play a significant role in determining the thickness and properties of ISW. Moreover, the key factor in basal melting was the northward movement of meltwater from intense ice melting regions near the grounding line. This movement determined the spatial distribution of ocean temperature and salinity. The horizontal gradient of ocean temperature and salinity induces mixing and horizontal intrusion. Interestingly, these mixing and intrusion phenomena occur in opposite directions, resulting in a wiggling pattern in the velocity profile. The main findings of our study will contribute to the formulation of a parameterization for basal melting, which can be incorporated into large-scale ocean models or ice sheet dynamics models. Direction and magnitude of ocean currents beneath an Larsen C ice shelf affect the ice shelf water thickness and propertiesNorthward meltwater advection causes 0.052 degrees C difference of thermal drivings with different melt rates far from and near the grounding lineOcean heat intrusion to ice shelf base is induced by Ekman dynamics and thermohaline interleaving by tilted isopycnals