The possibility that a deep mantle plume manifests Pliocene and Quaternary volcanism and potential elevated heat flux in West Antarctica has been studied for more than 30 years. Recent seismic images support the plume hypothesis as the cause of Marie Byrd Land (MBL) volcanism and geophysical structure. Mantle plumes may more than double the geothermal heat flux above nominal continental values. A dearth of in situ ice sheet basal data exists that samples the heat flux. Consequently, we examine a realistic distribution of heat flux associated with a possible late Cenozoic mantle plume in West Antarctica and explore its impact on thermal and melt conditions at the ice sheet base. We use a simple analytical mantle plume parameterization to produce geothermal heat flux at the base of the ice sheet. The three-dimensional ice flow model includes an enthalpy framework and full-Stokes stress balance. As both the putative plume location and extent are uncertain, we perform broadly scoped experiments to characterize the impact of the plume on geothermal heat flux and ice sheet basal conditions. The experiments show that mantle plumes have an important local impact on the ice sheet, with basal melting rates reaching several centimeters per year directly above the hotspot. In order to be consistent with observations of basal hydrology in MBL, the upper bound on the plume-derived geothermal heat flux is 150 mW/m2. In contrast, the active lake system of the lower part of Whillans Ice Stream suggests a widespread anomalous mantle heat flux, linked to a rift source.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017JB014423

Influence of a West Antarctic mantle plume on ice sheet basal conditions

Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography

. A classical Green's function approach for computing gravitationally consistent sea-level variations associated with mass redistribution on the earth's surface employed in contemporary sea-level models naturally suits the spectral methods for numerical evaluation. The capability of these methods to resolve high wave number features such as small glaciers is limited by the need for large numbers of pixels and high-degree (associated Legendre) series truncation. Incorporating a spectral model into (components of) earth system models that generally operate on a mesh system also requires repetitive forward and inverse transforms. In order to overcome these limitations, we present a method that functions efficiently on an unstructured mesh, thus capturing the physics operating at kilometer scale yet capable of simulating geophysical observables that are inherently of global scale with minimal computational cost. The goal of the current version of this model is to provide high-resolution solid-earth, gravitational, sea-level and rotational responses for earth system models operating in the domain of the earth's outer fluid envelope on timescales less than about 1 century when viscous effects can largely be ignored over most of the globe. The model has numerous important geophysical applications. For example, we compute time-varying computations of global geodetic and sea-level signatures associated with recent ice-sheet changes that are derived from space gravimetry observations. We also demonstrate the capability of our model to simultaneously resolve kilometer-scale sources of the earth's time-varying surface mass transport, derived from high-resolution modeling of polar ice sheets, and predict the corresponding local and global geodetic signatures.

/pdf/issm-sesaw-v1-0-mesh-based-computation-of-gravitationally-5473axyzmj.pdf

ISSM-SESAW v1.0: mesh-based computation of gravitationally consistent sea-level and geodetic signatures caused by cryosphere and climate driven mass change

Subglacial lakes are repositories of ancient climate conditions, provide habitats for life and modulate ice flow, basal hydrology, biogeochemical fluxes and geomorphic activity. In this Review, we construct the first global inventory of subglacial lakes (773 in total), which includes 675 from Antarctica (59 newly identified), 64 from Greenland, 2 beneath the Devon Ice Cap, 6 beneath Iceland’s ice caps and 26 from valley glaciers. This inventory is used to evaluate subglacial lake environments, dynamics and their wider impact on ice flow and sediment transport. The behaviour of these lakes is conditioned by their subglacial setting and the hydrological, dynamic and mass balance regime of the overlying ice mass. Regions where climate warming causes ice surface steepening are predicted to have fewer and smaller lakes, but increased activity with higher discharge drainages of shorter duration. Coupling to surface melt and rainfall inputs will modulate fill–drain cycles and seasonally enhance oxic processes. Higher discharges cause large, transient ice flow accelerations but might result in overall net slowdown owing to the development of efficient subglacial drainage. Subglacial lake research requires new drilling technologies and the integration of geophysics, satellite monitoring and numerical modelling to provide insight into the wider role of subglacial lakes in the changing Earth system. Subglacial lakes modify glacial conditions and flow. This Review provides a first global inventory of subglacial lakes, as well as outlining their settings, impacts and potential changes with climate warming. 

/pdf/subglacial-lakes-and-their-changing-role-in-a-warming-2zf2dcl2.pdf

Subglacial lakes and their changing role in a warming climate

We present a refined map of geothermal heat flow for Antarctica, Aq1, based on multiple observables. The map is generated using a similarity detection approach by attributing observables from geophysics and geology to a large number of high‐quality heat flow values (N = 5,792) from other continents. Observables from global, continental, and regional datasets for Antarctica are used with a weighting function that allows the degree of similarity to increase with proximity and how similar the observables are. The similarity detection parameters are optimized through cross correlation. For each grid cell in Antarctica, a weighted average heat flow value and uncertainty metrics are calculated. The Aq1 model provides higher spatial resolution in comparison to previous results. High heat flow is shown in the Thwaites Glacier region, with local values over 150 mW m−2. We also map elevated values over 80 mW m−2 in Palmer Land, Marie Byrd Land, Victoria Land and Queen Mary Land. Very low heat flow is shown in the interior of Wilkes Land and Coats Land, with values under 40 mW m−2. We anticipate that the new geothermal heat flow map, Aq1, and its uncertainty bounds will find extended use in providing boundary conditions for ice sheet modeling and understanding the interactions between the cryosphere and solid Earth. The computational framework and open architecture allow for the model to be reproduced, adapted and updated with additional data, or model subsets to be output at higher resolution for regional studies.

/pdf/antarctic-geothermal-heat-flow-model-aq1-jo48gcsw9w.pdf

Antarctic Geothermal Heat Flow Model: Aq1

Subglacial lakes have long been considered hydraulically isolated water bodies underneath ice sheets. This view changed radically with the advent of repeat-pass satellite altimetry and the discover...

https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2014.0296

Malte Thoma

Papers

Advances in modelling subglacial lakes and their interaction with the Antarctic ice sheet