Potential Ice Sheet Modulation of Volcanism in West Antarctica: Constraints on the Cadence and Magnitude of Melt Delivery Into the Crust

Variations in continental ice mass related to changes in Earth's obliquity can modulate volcanism. At Marie Byrd Land, increases in crustal temperature related to the transfer of magmas and to the insulating effects of the West Antarctic Ice Sheet will reduce the effective viscosity of wall rocks, causing the volcanic response to be reduced in magnitude and delayed by up to $\sim$10.25 kyr. For sufficiently high levels of crustal warming, magma storage is enhanced such that there is a negligible volcanic response. Tephra layers correlated to Mount Berlin volcanism signal increases in the frequency of silicic eruptions following maxima in the rate of deglaciation over 0–40 ka (interval 1) and possibly 100–135 ka (interval 2). During interval 1, an increase in eruption frequency at $\approx$8 ka lags deglaciation by $\approx$6.5–9 kyr. An increase in volcanism at 110 ka, by contrast, may lag deglaciation by $\ge$10.25 kyr. We hypothesize that a decrease in lag time of $\sim$10 ka reflects a period of reduced crustal warming related to a waning mantle melt supply. Using thermal models of the effects of ice sheet insulation and a time-dependent magma supply on the viscoelastic response of rocks hosting volcanically active magma reservoirs, we show that a periodic magma supply can drive oscillations between rheological regimes favoring eruption or storage. With additional constraints on the regional geothermal heat flux and eruption rate at Mount Berlin, an evolving response between 110 and 8 ka is consistent with magma injections with a period of $\sim 10^6$ years.