Modelling of Kealey Ice Rise, Antarctica, reveals stable ice-flow conditions in East Ellsworth Land over millennia

Abstract

ABSTRACT. Flow at ice divides, their shape, size and internal structure depend not only on local conditions, but also on the flow regimes and past histories of the surrounding ice masses. Here we use field data from Kealey Ice Rise, Ellsworth Land, West Antarctica, in combination with flow modelling to investigate any possible signs of transients in the flow of the surrounding ice masses. Kealey Ice Rise shows linear surface features running parallel to its ridge in satellite imagery and a conspicuous layering in the ground-penetrating radar data known as double-peaked Raymond bumps. Through numerical modelling, by using an anisotropic full-Stokes thermomechanical flow solver, we analyse the evolution of Kealey Ice Rise and the timescales involved. We conclude that the features observed in the stratigraphy of Kealey Ice Rise require at least 3 ka of near-stationary flow conditions. However, we cannot exclude the possibility of a recent flow reorganization in the last century. We stress that the signs of stationary flow in radar stratigraphy observed in Kealey Ice Rise have been observed in other ice divides in the East Ellsworth Land area, suggesting stationary flow conditions over a millennial timescale in the region.

Evolution of Derwael Ice Rise in Dronning Maud Land, Antarctica, over the last millennia

“…The dependency on the along‐ridge slope also hampers a detailed comparison with other ice rises where the surface topography is often less well known. A gross comparison shows that the normalized amplitudes (both depth and amplitude normalized to the local ice thickness) observed here are larger than at Roosevelt Island [ Martín et al , ], Siple Dome [ Nereson and Raymond , ], Halvfarryggen Ice Dome [ Drews et al , ], and Kealey Ice Rise [ Martín et al , ]), and comparable to Fletcher Promotory [ Hindmarsh et al , ], and Fuchs Piedmont [ Martín et al , ].…”

Ice‐flow reorganization in West Antarctica 2.5 kyr ago dated using radar‐derived englacial flow velocities

“…Ice‐core data covering the last 1 kyr from Berkner Island (Figure a) indicate approximately constant accumulation rates over this period [ Mulvaney et al , ], although previously higher accumulation would cause us to overestimate the age of the Raymond arches and previously lower accumulation would cause us to underestimate their age. Ice‐fabric evolution enhances the Raymond Effect over time [e.g., Pettit et al , ; Martín et al , , ], so the double‐arch structure in the vertical velocity field (Figure a), which is consistent with ice‐fabric development [ Martín et al , ], may indicate that the Raymond Effect was weaker in the past, causing us to underestimate the age of the arches.…”

Origin and dynamic significance of longitudinal structures ("flow stripes") in the Antarctic Ice Sheet

“…If this is the case, the basic elements of the flow configuration have been stable since the end of the last glacial cycle and through the entire Holocene. In support of this conclusion we note that (1) continental-shelf landforms deposited by an expanded Antarctic Ice Sheet indicate prolonged periods of sediment delivery focused at the mouths of glacial troughs, creating trough-mouth fans with several hundred metres of sediment, implying that these areas have been occupied by fast-flowing glaciers and ice streams for tens of millennia (Dowdeswell et al, 2003(Dowdeswell et al, , 2008, or even tens of millions of years, as in the case of the Lambert Glacier-Amery Ice Shelf system Hambrey et al, 1991;Taylor et al, 2004); (2) numerical ice-sheet modelling studies (Pollard and DeConto, 2009) and evidence from blue-ice areas indicate that the central dome and overall patterns of ice flow in the West Antarctic Ice Sheet have remained intact for > 200 000 years (Fogwill et al, 2012); and (3) radarstratigraphic studies indicate near-stationary flow conditions over millennia near major ice divides (Ross et al, 2011) and locally at ice rises (Martín et al, 2014).…”

“…4). After mapping and describing the pattern of surface features on the Antarctic Ice Sheet, we discuss their possible origin in relation to these three hypotheses and consider their relationship with internal ice-sheet features, such as buckled layers and folds inferred from radar studies (Conway et al, 2002;Campbell et al, 2008;Ross et al, 2011;Martín et al, 2014).…”