http://hdl.handle.net/11122/9723 2026-04-17T02:39:26Z http://hdl.handle.net/11122/16231 Calving as a source of acute and persistent kinetic energy to enhance submarine melting of tidewater glaciers Shaya, M. F.; Nash, J. D.; Pettit, E. C.; Amundson, Jason M.; Jackson, R. H.; Sutherland, D. A.; Winters, D. Calving icebergs at tidewater glaciers release large amounts of potential energy. This energy—in principle—could be a source for submarine melting, which scales with near‐terminus water temperature and velocity. Because near‐terminus currents are challenging to observe or predict, submarine melt remains a key uncertainty in projecting tidewater glacier retreat and sea level rise. Here, we study one submarine calving event at Xeitl Sít’ (LeConte Glacier), Alaska, to explore the effect of calving on ice melt, using a suite of autonomously deployed instruments beneath, around, and downstream of the calving iceberg. Our measurements captured flows exceeding 5 m/s and demonstrate how potential energy converts to kinetic energy (EK). While most energy decays quickly (through turbulence, mixing, and radiated waves), near‐terminus EK remains elevated, nearly doubling predicted melt rates for hours after the event. Calving-induced currents could thus be an important overlooked energy source for submarine melt and glacier retreat. 2025-10-07T00:00:00Z http://hdl.handle.net/11122/16230 Fine-scale variability in iceberg velocity fields and implications for an ice-associated pinniped Kaluzienski, Lynn M.; Amumdson, Jason M.; Womble, Jamie N.; Bliss, Andrew K.; Pearson, Linnea E. Icebergs found in proglacial fjords serve as important habitats for pinnipeds in polar and subpolar regions. Environmental forcings can drive dramatic changes in the overall reduction in ice coverage across fjords in the circumpolar regions, with implications for pinnipeds that use ice for critical life-history functions, including pupping and molting. To better understand how pinnipeds respond to changes in iceberg habitat, we combine (i) iceberg velocity fields over hourly to monthly timescales, derived from high-rate time-lapse photogrammetry of Johns Hopkins Glacier and Inlet, Alaska, with (ii) aerial photographic surveys of harbor seals (Phoca vitulina richardii) conducted during the pupping (June) and molting (August) seasons. Iceberg velocities typically followed a similar diurnal pattern: flow was weak and variable in the morning and strong and unidirectional in the afternoon. The velocity fields tended to be highly variable in the inner fjord across a range of timescales due to changes in the strength and location of the subglacial outflow, whereas, in the outer fjord, the flow was more uniform, and eddies consistently formed in the same locations. During the pupping season, seals were generally more dispersed across the slow-moving portions of the fjord (with iceberg speeds of < 0:2 ms−1). In contrast, during the molting season, the seals were increasingly likely to be found on fastmoving icebergs in or adjacent to the glacier outflow plume. The use of slow-moving icebergs during the pupping season likely provides a more stable ice platform for nursing, caring for young, and avoiding predators. Periods of strong glacier runoff and/or katabatic winds may result in more dynamic and less stable ice habitats, with implications for seal behavior and distribution within the fjord. 2025-06-24T00:00:00Z http://hdl.handle.net/11122/16229 Laboratory experiments reveal transient fluctuations in ice mélange velocity and stress during periods of quasistatic flow Nissanka, Kavinda; Vora, Nandish; Méndez Harper, Joshua; Burton, Justin C.; Amundson, Jason M.; Robel, Alexander A.; Meng, Yue; Lai, Ching-Yao Accurately predicting Greenland's ice mass loss is crucial for understanding future sea level rise. Approximately 50% of the mass loss results from iceberg calving at the ice-ocean interface. Ice mélange, a jammed, buoyant granular material that extends for 10 km or more in Greenland's largest fjords, can inhibit iceberg calving and discharge by transmitting shear stresses from fjord walls to glacier termini. Direct measurements of these resistive force dynamics are not possible in the field, thus, we created a scaled-down laboratory experiment to study jammed-packed ice mélange mechanics. We recorded videos of the mélange surface motion and subsurface profile during slow, quasistatic flow through a rectangular fjord, and recorded the total force on a model glacier terminus. When the wall friction is low, the ice mélange moves as a solid plug with little or no particle rearrangements. When the wall friction is larger than the internal friction, shear zones develop near the walls, and the buttressing force magnitude and fluctuations increase significantly. Associated discrete particle simulations illustrate the internal flow in both regimes. We also compare our experimental results to a continuum, depth-averaged model of ice mélange and find that the thickness of the mélange at the terminus provides a good indicator of the net buttressing force. However, the continuum model cannot capture the stochastic nature of the rearrangements and concomitant fluctuations in the buttressing force. These fluctuations may be important for short-time and seasonal controls on iceberg calving rates in fjords with thick and persistent ice mélange. 2025-09-01T00:00:00Z http://hdl.handle.net/11122/15715 A quasi-one-dimensional ice mélange flow model based on continuum descriptions of granular materials Amundson, Jason M.; Robel, Alexander A.; Burton, Justin C.; Nissanka, Kavinda Field and remote sensing studies suggest that ice mélange influences glacier–fjord systems by exerting stresses on glacier termini and releasing large amounts of freshwater into fjords. The broader impacts of ice mélange over long timescales are unknown, in part due to a lack of suitable ice mélange flow models. Previous efforts have included modifying existing viscous ice shelf models, despite the fact that ice mélange is fundamentally a granular material, and running computationally expensive discrete element simulations. Here, we draw on laboratory studies of granular materials, which exhibit viscous flow when stresses greatly exceed the yield point, plug flow when the stresses approach the yield point, and exhibit stress transfer via force chains. By implementing the nonlocal granular fluidity rheology into a depth- and width-integrated stress balance equation, we produce a numerical model of ice mélange flow that is consistent with our understanding of well-packed granular materials and that is suitable for long-timescale simulations. For parallel-sided fjords, the model exhibits two possible steady-state solutions. When there is no calving of icebergs or melting of previously calved icebergs, the ice mélange is pushed down-fjord by the advancing glacier terminus, the velocity is constant along the length of the fjord, and the thickness profile is exponential. When calving and melting are included and treated as constants, the ice mélange evolves into another steady state in which its location is fixed relative to the fjord walls, the thickness profile is relatively steep, and the flow is extensional. For the latter case, the model predicts that the steady-state ice mélange buttressing force depends on the surface and basal melt rates through an inverse power-law relationship, decays roughly exponentially with both fjord width and gradient in fjord width, and increases with the iceberg calving flux. The buttressing force appears to increase with calving flux (i.e., glacier thickness) more rapidly than the force required to prevent the capsizing of full-glacier-thickness icebergs, suggesting that glaciers with high calving fluxes may be more strongly influenced by ice mélange than those with small fluxes. 2025-01-08T00:00:00Z