Many icy moons in the outer Solar System host large subsurface oceans maintained by tidal heating (Nimmo & Pappalardo, 2016), and are considered the most likely bodies in our Solar System to host habitable environments (Domagal-Goldman et al., 2016;Gaidos et al., 1999). The upcoming JUICE and Europa Clipper missions will specifically target the habitability of Jupiter's moon Europa (Grasset et al., 2013;Howell & Pappalardo, 2020). One major unknown is the source of oxidants that are necessary to generate and maintain redox gradients within its ocean (

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The habitability of oceans within icy worlds depends on material and heat transport through their outer ice shells. Previous work shows a methane clathrate layer at the upper surface of the ice shell of Titan thickens the convecting region, while on Pluto a clathrate layer at the base of the ice shell hinders convection. In this way, the dynamics of clathrate‐ice shells may be essential to the thermal evolution and habitability of ocean worlds. However, studies to date have not addressed the dynamics that determine the location of clathrates within the ice shell. Here, we show that, in contrast to previous studies, clathrates accumulating at the base of the ice shell are entrained throughout the shell. Clathrates are stiffer than ice. As a result, entrainment slows convection and thickens the conductive lid across a range of ocean worlds, potentially preserving sub‐ice oceans but limiting avenues for material transport into them.

Abstract. We use a simplified glacier-landscape model to investigate the degree to which basin topography, climate regime, and vegetation succession impact centennial variations in basin runoff during glacier retreat. In all simulations, annual basin runoff initially increases as water is released from glacier storage but ultimately decreases to below preretreat levels due to increases in evapotranspiration and decreases in orographic precipitation. We characterize the long-term (> 200 years) annual basin runoff curves with four metrics: the magnitude and timing of peak basin runoff, the time to preretreat basin runoff, and the magnitude of end basin runoff. We find that basin slope and climate regime have strong impacts on the magnitude and timing of peak basin runoff. Shallow sloping basins exhibit a later and larger peak basin runoff than steep basins and, similarly, continental glaciers produce later and larger peak basin runoff compared to maritime glaciers. Vegetation succession following glacier loss has little impact on the peak basin runoff but becomes increasingly important as time progresses, with more rapid and extensive vegetation leading to shorter times to preretreat basin runoff and lower levels of end basin runoff. We suggest that differences in the magnitude and timing of peak basin runoff in our simulations can largely be attributed to glacier dynamics: glaciers with long response times (i.e., those that respond slowly to climate change) are pushed farther out of equilibrium for a given climate forcing and produce larger variations in basin runoff than glaciers with short response times. Overall, our results demonstrate that glacier dynamics and vegetation succession should receive roughly equal attention when assessing the impacts of glacier mass loss on water resources.

Abstract. The dynamic loss of ice via outlet glaciers around the Greenland Ice Sheet is a major contributor to sea level rise. However, the retreat history and ensuing dynamic mass loss of neighboring glaciers are disparate, complicating projections of sea level rise. Here, we examine the stress balance evolution for three neighboring glaciers prior to; at the onset of; during; and, where possible, after retreat. We find no dynamic or thickness changes preceding retreat, implicating a retreat trigger at the ice–ocean boundary. Terminus retreat initiates large-scale changes in the stress state at the terminus. This includes a drop in along-flow resistance to driving stress followed by an increase in lateral drag and associated glacier acceleration. We find that the pre-retreat spatial pattern in stresses along-fjord may control retreat duration and thus the long-term dynamic response of a glacier to terminus retreat. Specifically, glaciers with large regions of low basal drag extending far inland from the terminus permit a chain of stress changes that results in sustained acceleration, increased mass loss, and continued retreat. Glaciers with similarly low basal stress conditions occur around Greenland. Our results suggest that for such glaciers, dynamic mass loss can be sustained into the future despite a pause in ocean forcing.

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Abstract. We couple a glacier flow model to a simplified landscape model to investigate the effects of glacier dynamics, climate, and vegetation succession on annual basin runoff during glacier retreat. Basin runoff initially increases as water is released from glacier storage but eventually decreases to below preretreat levels due to increases in evapotranspiration and altitudinal losses in precipitation. Peak basin runoff and the time to peak basin runoff are primarily determined by glacier dynamics, with shallow sloping continental glaciers experiencing the largest increases in basin runoff (up to 62 %) and longest time until peak basin runoff (up to 142 years), compared to 14 % and 54 years for steep maritime glaciers subjected to the same rate of climate change. These differences in peak basin runoff and time to peak basin runoff can be characterized by the glacier response time: glaciers with long response times are pushed farther out of equilibrium for a given climate forcing and produce larger variations in basin runoff than glaciers with short response times. After peak basin runoff is reached, vegetation plays an increasingly important role, with basin runoff decreasing considerably faster for heavily vegetated landscapes than for rocky landscapes and ultimately reaching values that are over 50 % lower than preretreat levels. Our results demonstrate that glacier dynamics and landscape evolution should receive roughly equal attention when assessing the impacts of glacier mass loss on water resources.