6 research outputs found
Meltwater Intrusions Reveal Mechanisms for Rapid Submarine Melt at a Tidewater Glacier
Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but to date melting has been difficult to observe and quantify. As a result, melt rates have been estimated from parameterizations that are largely unconstrained by observations, particularly at the near-vertical termini of tidewater glaciers. With standard coefficients, these melt parameterizations predict that ambient
melting (the melt away from subglacial discharge outlets) is negligible compared to discharge-driven melting for typical tidewater glaciers. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe ambient meltwater intrusions that are ubiquitous within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Our results suggest that ambient melt rates are substantially higher (Ă—100) than standard theory predicts and that ambient melting is a significant part of the total submarine melt flux. We explore modifications to the prevalent melt parameterization to provide a path forward for improved modeling of ocean-glacier interactions.This work was funded by NSF OPP Grants 1503910, 1504191, 1504288,
and 1504521 and National Geographic Grant CP4-171R-17. Additionally, this research was supported by the NOAA Climate and Global Change Postdoctoral Fellowship Program, administered by UCAR’s Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award #NA18NWS4620043B. These observations would not be possible without the skilled engineering team who developed the autonomous kayaks—including Jasmine Nahorniak, June Marion, Nick McComb, Anthony Grana, and Corwin Perren—and also the Captain and crew of the M/V Amber Anne. We thank Donald Slater and an anonymous reviewer for valuable feedback that improved this manuscript. Data availability: All of the oceanographic data collected by ship and kayak have been archived with the National Centers for Environmental Information (Accession 0189574, https://accession.nodc.noaa.gov/ 0189574). The glacier data have been archived at the Arctic Data Center (https://doi.org/10.18739/A22G44).Ye
Direct observations of submarine melt and subsurface geometry at a tidewater glacier
Ice loss from the world’s glaciers and ice sheets contributes to sea level rise, influences
ocean circulation, and affects ecosystem productivity. Ongoing changes in glaciers and
ice sheets are driven by submarine melting and iceberg calving from tidewater glacier
margins.Ice loss from the world’s glaciers and ice sheets contributes to sea level rise, influences
ocean circulation, and affects ecosystem productivity. Ongoing changes in glaciers and
ice sheets are driven by submarine melting and iceberg calving from tidewater glacier
margins. However, predictions of glacier change largely rest on unconstrained theory for
submarine melting. Here, we use repeat multibeam sonar surveys to image a subsurface
tidewater glacier face and document a time-variable, three-dimensional geometry linked
to melting and calving patterns. Submarine melt rates are high across the entire ice face over
both seasons surveyed and increase from spring to summer. The observed melt rates are up
to two orders of magnitude greater than predicted by theory, challenging current simulations of
ice loss from tidewater glaciers.Department of Earth Sciences, University of Oregon,
Eugene, OR 97403, USA. 2
College of Earth, Ocean, and
Atmospheric Sciences, Oregon State University, Corvallis, OR
97331, USA. 3
Department of Natural Sciences, University of
Alaska Southeast, Juneau, AK 99801, USA. 4
Institute for
Geophysics, University of Texas at Austin, Austin, TX 78758,
USA. 5
Department of Marine Sciences, University of North
Carolina, Chapel Hill, NC 27599, USA. 6
Geophysical Institute,
University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
*Corresponding author. Email: [email protected]
†Present address: Department of Marine and Coastal Sciences,
Rutgers University, New Brunswick, NJ 08901, USA.Ye