Fine-scale spatial segregation in a pelagic seabird driven by differential use of tidewater glacier fronts

In colonially breeding marine predators, individual movements and colonial segregation are influenced by seascape characteristics. Tidewater glacier fronts are important features of the Arctic seascape and are often described as foraging hotspots. Albeit their documented importance for wildlife, little is known about their structuring effect on Arctic predator movements and space use. In this study, we tested the hypothesis that tidewater glacier fronts can influence marine bird foraging patterns and drive spatial segregation among adjacent colonies. We analysed movements of black-legged kittiwakes (Rissa tridactyla) in a glacial fjord by tracking breeding individuals from five colonies. Although breeding kittiwakes were observed to travel up to ca. 280 km from the colony, individuals were more likely to use glacier fronts located closer to their colony and rarely used glacier fronts located farther away than 18 km. Such variation in the use of glacier fronts created fine-scale spatial segregation among the four closest (ca. 7 km distance on average) kittiwake colonies. Overall, our results support the hypothesis that spatially predictable foraging patches like glacier fronts can have strong structuring effects on predator movements and can modulate the magnitude of intercolonial spatial segregation in central-place foragers.

A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving

We present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland from the terminus and up to 41 and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year in which Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between types of behaviour. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store Glacier.

Assessing Controls on Ice Dynamics at Crane Glacier, Antarctic Peninsula Using a Numerical Ice Flow Model

The widespread retreat of glaciers and the collapse of ice shelves along the Antarctic Peninsula has been attributed to atmospheric and oceanic warming, which promotes mass loss. However, several glaciers on the eastern peninsula that were buttressed by the Larsen A and B ice shelves prior to collapse in 1995 and 2002, respectively, have been advancing in recent years. This asymmetric pattern of rapid retreat and long-term re-advance is similar to the tidewater glacier cycle, which can occur largely independent of climate forcing. Here, I use a width- and depth-integrated numerical ice flow model to investigate glacier response to ice shelf collapse and the influence of changing climate conditions at Crane Glacier, formerly a tributary of the Larsen B ice shelf, over the last ~10 years. Sensitivity tests to explore the influence of perturbations in surface mass balance and submarine melt (up to 10 m a-1) and fresh water impounded in crevasses (up to 10 m) on glacier dynamics reveal that by 2100, the modeled mass discharge ranges from 0.53-98 Gt a-1, with the most substantial changes due to surface melt-induced thinning. My findings suggest that the growth of a floating ice tongue can hinder enhanced flow, allowing the grounding zone to remain steady for many decades, analogous to the advancing stage of the tidewater glacier cycle. Additionally, former tributary glaciers can take several decades to geometrically adjust to ice shelf collapse at their terminal boundary while elevated glacier discharge persists.

A fully-coupled 3D model of a large Greenlandic outlet glacier with evolving subglacial hydrology, frontal plume melting and calving

We present the first fully coupled 3D full-Stokes model of a tidewater glacier, incorporating ice flow, subglacial hydrology, plume-induced frontal melting and calving. We apply the model to Store Glacier (Sermeq Kujalleq) in west Greenland to simulate a year of high melt (2012) and one of low melt (2017). In terms of modelled hydrology, we find perennial channels extending 5 km inland fromthe terminus and up to 41 km and 29 km inland in summer 2012 and 2017, respectively. We also report a hydrodynamic feedback that suppresses channel growth under thicker ice inland and allows water to be stored in the distributed system. At the terminus, we find hydrodynamic feedbacks exert a major control on calving through their impact on velocity. We show that 2012 marked a year inwhich Store Glacier developed a fully channelised drainage system, unlike 2017, where it remained only partially developed. This contrast in modelled behaviour indicates that tidewater glaciers can experience a strong hydrological, as well as oceanic, control, which is consistent with observations showing glaciers switching between seemingly dominant types. The fully coupled nature of the model allows us to demonstrate the likely lack of any hydrological or ice-dynamic memory at Store.

Glacimarine sediment flows in small bays on the Danco Coast, Antarctic Peninsula

Global atmospheric warming and rising ocean temperatures can contribute to the acceleration of glacier melting and influence the generation and physical characteristics of sediment flows in bays and fjords of the Antarctic Peninsula. During the First Scientific Expedition of Colombia to the Antarctic, carried out between January and February 2015, hydrographic variables (temperature, salinity, pressure and turbidity) were measured in the water column, from very close to the main glacier front towards the offshore, on 5 bays of the Danco Coast, Western Antarctic Peninsula. Glacimarine sediment plumes from the tidewater glacier were identified in all bays, however, with varying spatial extensions as well as the concentration of sediments, being those of the central area of the Danco Coast, the most extensive and concentrated. By comparison with previous years, in this work higher average particle concentrations were recorded. The greater flow of glaciomarine sediments could be associated with greater glacial melting, among other possible factors

Harbor Seals as Sentinels of Ice Dynamics in Tidewater Glacier Fjords

Tidewater glaciers calve icebergs into the marine environment which serve as pupping, molting, and resting habitat for some of the largest seasonal aggregations of harbor seals (Phoca vitulina richardii) in the world. Although they are naturally dynamic, advancing and retreating in response to local climatic and fjord conditions, most tidewater glaciers around the world are thinning and retreating. Climate change models predict continued loss of land-based ice with unknown impacts to organisms such as harbor seals that rely on glacier ice as habitat for critical life history events. To understand the impacts of changing ice availability on harbor seals, we quantified seasonal and annual changes in ice habitat in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park in southeastern Alaska. We conducted systematic aerial photographic surveys (n = 55) of seals and ice during the pupping (June; n = 30) and molting (August; n = 25) periods from 2007 to 2014. Object-based image analysis was used to quantify the availability and spatial distribution of floating ice in the fjord. Multivariate spatial models were developed for jointly modeling stage-structured seal location data and ice habitat. Across all years, there was consistently more ice in the fjord during the pupping season in June than during the molting season in August, which was likely driven by seasonal variation in physical processes that influence the calving dynamics of tidewater glaciers. Non-pup harbor seals and ice were correlated during the pupping season, but this correlation was reduced during the molting season suggesting that harbor seals may respond to changes in habitat differently depending upon trade-offs associated with life history events, such as pupping and molting, and energetic costs and constraints associated with the events.