ACTIVE-RECENT SUBGLACIAL VOLCANISM WITHIN THE WEST ANTARCTIC RIFT SYSTEM, INTERPRETED FROM AEROMAGNETIC AND RADAR ICE SOUNDING MAY EFFECT THE STABILITY OF THE WEST ANTARCTIC ICE SHEET (WAIS) WHICH FLOWS THROUGH IT

Aeromagnetic and radar ice sounding surveys of the volcanically active West Antarctic rift system indicate >1000 high-amplitude, shallow-source, magnetic anomalies over a >500,000 km² area interpreted as caused by subglacial volcanic rocks beneath the WAIS. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys carried out in the past two decades characterize the magnetic field and bed topography. These 5-50-km width, magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice. Behrendt et al., (2005, 2008) interpreted these anomalies as indicating "volcanic centers." requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction; >80% of the anomaly sources at the bed of the WAIS, have been modified by the moving ice into which they were injected, requiring a younger age than the WAIS. Behrendt et al., (1994; 2007) conservatively estimated >1 x 10⁶ km³ volume of volcanic sources to account for the area of the "volcanic center" anomalies and suggested a large igneous province (LIP) if this volume was intruded within 1-10 m.y. Although exposed volcanoes surrounding the WAIS extend in age to ~34 Ma, Mt Erebus, (<1 Ma) Mt. Melbourne, (<0.26 Ma), and Mt. Takahe (<0.1 Ma) are examples of exposed active volcanoes there. However, the great volume of volcanic centers is buried beneath the WAIS. If only a very small percentage of these >1000 volcanic, magnetic-anomaly sources is active, subglacial volcanism may affect the dynamics of the WAIS. Interpreted active subglacial volcanism is revealed by aerogeophysical data reported by Blankenship et al., (1993, Mt. Casertz), and Corr and Vaughan, (2008, near Hudson Mts.). Wingham et al. (2009) reported an average rate of volume loss from 2.6 to 10.1 km³ /yr from 1995 to 2006 for the Pine Island Glacier (PIG) near the Hudson Mts. Jenkins et al. (2010) reported new evidence of acceleration of the PIG. Even if there is a very low probability, future effects on the stability of the WAIS and associated sea-level rise should not be ignored, as the rapid changes observed in the past 20 years resulting from global warming, could be accelerated by subglacial volcanism.