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Madison Smith

Postdoctoral Scholar

Email

mmsmith@apl.uw.edu

Phone

206-616-5736

Department Affiliation

Polar Science Center

Education

B.A. Earth & Oceanographic Science and Environmental Studies, Bowdoin College, 2014

B.S. Civil & Environmental Engineering, University of Washington, 2016

Ph.D. Civil Engineering, University of Washington, 2019

Publications

2000-present and while at APL-UW

Wave-driven flow along a compact marginal ice zone

Thomson, J., B. Lund, J. Hargrove, M.M. Smith, J. Horstmann, and J.A. MacKinnon, "Wave-driven flow along a compact marginal ice zone," Geophys. Res. Lett., EOR, doi:10.1029/2020GL090735, 2021.

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19 Jan 2021

Observations of surface waves and ice drift along a compact sea ice edge demonstrate the importance of waves in a marginal ice zone. An analytic model is presented for the along‐ice drift forced by the radiation stress gradient of oblique waves. A momentum balance using quadratic drag to oppose the wave forcing is sufficient to explain the observations. Lateral shear stresses in the ice are also evaluated, though this balance does not match the observations as well. Additional forcing by local winds is included and is small relative to the wave forcing. However, the wave forcing is isolated to a narrow region around 500‐m wide, whereas the wind forcing has effects on larger scales. The simplistic drag is assessed using observations of shear and turbulent dissipation rates. The results have implications for the shape and evolution of the ice edge, because the lateral shear may be a source of instabilities.

Frazil ice growth and production during katabatic wind events in the Ross Sea, Antarctica

Thompson, L., M. Smith, J. Thomson, S. Stammerjohn, S. Ackley, and B. Loose, "Frazil ice growth and production during katabatic wind events in the Ross Sea, Antarctica," Cryosphere, 14, 3329-3347, doi:10.5194/tc-14-3329-2020, 2020.

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6 Oct 2020

Katabatic winds in coastal polynyas expose the ocean to extreme heat loss, causing intense sea ice production and dense water formation around Antarctica throughout autumn and winter. The advancing sea ice pack, combined with high winds and low temperatures, has limited surface ocean observations of polynyas in winter, thereby impeding new insights into the evolution of these ice factories through the dark austral months. Here, we describe oceanic observations during multiple katabatic wind events during May 2017 in the Terra Nova Bay and Ross Sea polynyas. Wind speeds regularly exceeded 20 m s-1, air temperatures were below –25°C, and the oceanic mixed layer extended to 600 m. During these events, conductivity–temperature–depth (CTD) profiles revealed bulges of warm, salty water directly beneath the ocean surface and extending downwards tens of meters. These profiles reflect latent heat and salt release during unconsolidated frazil ice production, driven by atmospheric heat loss, a process that has rarely if ever been observed outside the laboratory. A simple salt budget suggests these anomalies reflect in situ frazil ice concentration that ranges from 13 to 266x10-3 kg m-3. Contemporaneous estimates of vertical mixing reveal rapid convection in these unstable density profiles and mixing lifetimes from 7 to 12 min. The individual estimates of ice production from the salt budget reveal the intensity of short-term ice production, up to 110 cm d-1 during the windiest events, and a seasonal average of 29 cm d-1. We further found that frazil ice production rates covary with wind speed and with location along the upstream–downstream length of the polynya. These measurements reveal that it is possible to indirectly observe and estimate the process of unconsolidated ice production in polynyas by measuring upper-ocean water column profiles. These vigorous ice production rates suggest frazil ice may be an important component in total polynya ice production.

Observations of exponential wave attenuation in Antarctic sea ice during the PIPERS campaign

Kohout, A.L., M. Smith, L.A. Roach, G. Williams, F. Montiel, and M.J.M. Williams, "Observations of exponential wave attenuation in Antarctic sea ice during the PIPERS campaign," Ann. Glaciol., 61, 196-209, doi:10.1017/aog.2020.36, 2020.

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1 Sep 2020

Quantifying the rate of wave attenuation in sea ice is key to understanding trends in the Antarctic marginal ice zone extent. However, a paucity of observations of waves in sea ice limits progress on this front. We deployed 14 waves-in-ice observation systems (WIIOS) on Antarctic sea ice during the Polynyas, Ice Production, and seasonal Evolution in the Ross Sea expedition (PIPERS) in 2017. The WIIOS provide in situ measurement of surface wave characteristics. Two experiments were conducted, one while the ship was inbound and one outbound. The sea ice throughout the experiments generally consisted of pancake and young ice < 0.5 m thick. The WIIOS survived a minimum of 4 d and a maximum of 6 weeks. Several large-wave events were captured, with the largest recorded significant wave height over 9 m. We find that the total wave energy measured by the WIIOS generally decays exponentially in the ice and the rate of decay depends on ice concentration.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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