In this thesis the sensitivity of the cryosphere to changing weather patterns in the Ross Sea is investigated. The focus is on the production and persistence of sea ice and precipitation events over the Ross Ice Shelf (RIS). Changes are expected as a result of climate variability, and the change in the occurrence of storms and other severe weather patterns in Antarctica and in the Ross Sea.

The influence of strong wind events on the sea ice concentration within the Ross Sea Polynya (RSP) is studied. Sea ice concentration within the RSP was observed to show a rapid decrease in response to strong wind events. Following a strong wind event, the RSP was found to remain open for an extended period of time, persisting beyond the end of the strong wind event. Sea ice drift within the Ross Sea was observed to be influenced by strong wind events with cyclonic drift anomalies being observed during periods of strong winds. A comparison of ERA-Interim reanalysis wind speeds and observed Automatic Weather Station (AWS) wind speeds east of Ross Island revealed that, despite strong correlations between the two data sets, ERA-Interim considerably underestimates wind speeds.

Data from a Controlled Meteorological balloon flight within the atmospheric boundary layer over the Ross Sea in November 2017 is presented. The flight lasted 70 hours and passed over both the Terra Nova Bay and Ross Sea polynyas whilst making 31 vertical soundings. Balloon observations of temperature, humidity, and wind velocity were compared to co-located predictions made by the Antarctic Mesoscale Prediction System (AMPS); the two data sets were gener- ally found to agree. The wind direction predictions made by AMPS were found to be least accurate in the vicinity of complex topography and during periods of low wind speed. The upward heat and moisture fluxes from the RSP were investigated. Lagrangian and Eulerian derivatives of potential temperature and water mixing ratios were calculated using Lagrangian back trajectories within the AMPS field. This allow sources and sinks of both heat and moisture to be identified. While diabatic heating was observed over the RSP during this period, the same area was not observed to provide a net flux of moisture.

The various circulation patterns that influence the rate of precipitation over the RIS are studied. The moisture origins for a site over the RIS were investigated using Lagrangian back trajectories. An ensemble of over 50 000 back trajectories were calculated using ERA-Interim wind field from 1979 until 2016. The spa- tial distributions of back trajectory origin points were compared for periods of precipitation and for periods without precipitation. During periods of precipitation, higher origin point densities were observed in the Ross and Amundsen Seas, and lower densities were observed in the Bellingshausen and Weddell Seas. The pathways taken by trajectories with similar origin locations to reach the RIS often show large variations. This was shown to have a dramatic effect on the humidity of the air parcel at arrival; trajectories that travel over mountainous regions were often very dry once they arrived over the RIS.

This thesis, therefore, has a strong focus on processes associated with the RSP. It is shown that strong winds over this region result in the advection of sea ice exposing the warm ocean below. This causes freezing of the ocean surface resulting in sea ice production in this region. The influence of this polynya on the local atmosphere was investigated. AMPS potential temperature fields indicate this region of open water provided a heat flux to the atmosphere over a 20 000 km2 area during the period of balloon observations. A moisture flux was not observed from AMPS water mixing ratio field for the same period. Sea ice isolates the atmosphere from the ocean preventing evaporation of moisture. Moisture trans- port to the RIS was found to be limited by sea ice, as moist air was generally found to originate from north of the ice pack.