Recent field investigations of a megadunes region of East Antarctica provide evidence that differences in grain size, thermal conductivity, and permeability across a megadune are due to relative accumulation patterns in the absence of significant variations in microclimate. The differences in accumulation patterns include distinct areas of perceptible but low accumulation (less than 40 mm w.eq.a^-1) and areas of accumulation hiatus within several kilometers proximity, as determined by remote sensing, surface feature classification, and GPR profiling. Near-surface firn properties are very sensitive to the amount of accumulation in low accumulation rate regions, with relatively small differences in accumulation rate (less than 40 mm w.eq.a ^-1) creating distinctive differences in grain size, thermal conductivity, and permeability, accompanied by variations in satellite-based microwave data from both passive and active sensors. Cores from the megadunes region exhibit variations in physical properties at depth due to temporal changes in local accumulation caused by dune migration. A new way of describing gas diffusivity and air permeability of polar firn is developed. Diffusivity-porosity and permeability-porosity power-law relationships vary from site to site with accumulation rate having the largest impact on the value of the exponent. The largest differences in firn properties occur between firn from hiatus sites compared to sites where any accumulation, from low to high values, occurs.