Candidates for volcanoes under the ice of Antarctica detected by their gravito-topographic signal

Jaroslav Klokocnik,Ivan Pesek,Jan Kostelecky,Ales Bezdek

doi:10.4401/ag-7427

Abstract

We analyse the newest gravity field models (given in the form of spherical harmonic expansion to degree and order 2190) EIGEN 6C4 and RET 14, which consist basically from the gravity data from EIGEN 6C4 plus the bedrock topography from the Bedmap 2 model, describing the topography of the ground under ice of Antarctica. From these models we computed the gravity anomalies, the Marussi tensor of the second derivatives of the disturbing potential, the gravity invariants and their specific ratio, the strike angle and the virtual deformations. We apply these results for a selected part of Antarctica; not too far from the Lake Vostok we discovered at least two objects that might be subglacial volcanoes. We present all predictors and arguments we have available to support this hypothesis, but we are well aware that the “last word” waits for other specialists. We provide geographic coordinates on the ice cover where to dig for the possible volcanoes.

Highlights

We use the best available gravity data and the bedrock topography data [Bedmap 2, Fretwell et al 2013] to detect possible subglacial volcanoes and other features
This paper is a continuation of Klokočník et al [2016]; it deals with possible subglacial volcanoes discovered near the Lake Vostok (LV)
We work with the bedrock topography; it is given in a network 1x1 km, but it does not mean that everywhere the topography data have such a resolution

Summary

Introduction

We use the best available gravity data (the harmonic geopotential coefficients from the gravity field model RET 14 [Hirt et al 2016], focused on Antarctica, transformed to the various gravity functions) and the bedrock topography data [Bedmap 2, Fretwell et al 2013] to detect possible subglacial volcanoes and other features (like subglacial lakes and rivers). The core of our method [Klokočník et al 2016, 2017b] is in the use of various gravitational (or gravity) aspects, namely the gravity anomalies or disturbances Δg, the components of the Marussi tensor Γ of the second derivatives Tij of the disturbing potential (especially the radial component Tzz), the gravity invariants I1 and I1, their specific ratio I, the strike angle θ and the virtual deformations vd. Each such gravity aspect contains different information and has a different sensitivity to the underlying causative density variations [see Figure 2 in Klokočník et al 2016]; the traditional gravity anomalies are already not sufficient, more gravity aspects are used. We work with the bedrock topography; it is given in a network 1x1 km (in a specific x,y coordinate frame of Bedmap 2), but it does not mean that everywhere the topography data have such a resolution (more about this topic is in Sections 2.1 and 2.2)

Notes on the data

Gravity symptoms of a single mountain from the gravity aspects

The results - Examples of possible subglacial volcanoes near the Lake Vostok

Candidates for volcanoes

Geodetic coordinates and suggested names of the candidates for volcanoes

Conclusion