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WIREs Clim Change
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Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

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Abstract The calving of A‐68, the 5,800‐km2, 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps. This article is categorized under: Climate, Ecology, and Conservation > Modeling Species and Community Interactions
Top, pre‐collapse. Bottom, post‐collapse. Shifts in the spatial and temporal ranges of pelagic and benthic organisms, populations, and communities post‐collapse lead to changes in trophic dynamics and species ranges, altering ecosystem properties, processes, and functions of sub‐ice‐shelf areas. Thin black arrows between pelagic and surface biota indicate trophic interactions. The color gradient of the particulate organic carbon flux indicates the change from fresh to more degraded/refractory material. Thicker arrows indicate higher fluxes. Reprinted with permission from Ingels et al. (2018)
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Expected changes in physical, pelagic biological, benthic‐pelagic, and benthic parameters following ice‐shelf collapse. Temporal scale corresponds with Figure 2; T0: ice‐shelf intact; T1: first year following collapse; T1–3: first 3 years following collapse; T3–10: 3–10 years following collapse; T10–30: 2–3 decades following collapse. Scale legend for each parameter appears on the right‐hand side. Shading indicates uncertainty and variability, which generally increases over time. Owing to the diverse conditions that exist across the Antarctic in different ice‐shelf regions and poor understanding of the ecological mechanisms and interactions between ecosystem components and processes, substantial uncertainty remains in predicting the different types and magnitudes of changes (cf. Section 4)
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Expected changes in ice‐shelf regions following ice‐shelf retreat and collapse. Visualized are surface blooms and primary production, organic matter flux to the seafloor and provision of the food bank (the pool of labile and refractory matter), and drop‐stone frequency. T0: During ice‐shelf cover, there is very low input of organic and inorganic food sources; primarily through advection from open water and limited chemosynthetic sources. T1 year: In the year following ice‐shelf collapse, an increase in drop‐stones is expected from increasing supply of glacial‐fed icebergs. Increased POC flux follows novel primary production and surface‐water blooms in the newly‐opened waters. T1–3 years: In the first years following ice‐shelf collapse seasonality in primary production is introduced, with high spatiotemporal variability. Shifts in plankton composition are likely, yielding mismatches and changes trickling through the pelagic and benthic food webs. Drop‐stone release continues, providing hard benthic substrates for new colonizers, but also disturbing the sediment. T3–10 years: Continued seasonal primary production feeds the benthic food bank resulting in increased biomass, potentially increasing diversity and shifting the composition of benthic assemblages. Increased glacial discharge may continue to deliver drop‐stones, and iceberg calving can cause scouring disturbance. Deposition of terrigenous material possibly increases. High temporal and spatial variability in the deposition of food and disturbance remains. T10–30 years: High spatial and temporal variability of POC fluxes and organism distributions remain but could be more widespread following continued warming and potential reduction in seasonal sea‐ice cover. Buildup of the food bank continues, with increased density and activity of organisms following enhanced food access. Increased bioturbation leads to increased oxygen penetration. However, oxygen penetration may shoal again if the flux of organic matter to the seafloor and subsequently organic matter deposition and biological activity increase. Image created by the Center for Environmental Visualization (CEV), University of Washington
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