Campus Map

Madison Smith

Research Assistant




2000-present and while at APL-UW

Episodic reversal of autumn ice advance caused by release of ocean heat in the Beaufort Sea

Smith, M., S. Stammerjohn, O. Persson, L. Rainville, G. Liu, W. Perrie, R. Robertson, J. Jackson, and J. Thomson, "Episodic reversal of autumn ice advance caused by release of ocean heat in the Beaufort Sea," J. Geophys. Res., 123, 3164-3185, doi:10.1002/2018JC013764, 2018.

More Info

1 May 2018

High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beaufort Sea demonstrate how stored ocean heat can be released to temporarily reverse seasonal ice advance. Strong on‐ice winds over a vast fetch caused mixing and release of heat from the upper ocean. This heat was sufficient to melt large areas of thin, newly formed pancake ice; an average of 10 MJ/m2 was lost from the upper ocean in the study area, resulting in ~3–5 cm pancake sea ice melt. Heat and salt budgets create a consistent picture of the evolving air‐ice‐ocean system during this event, in both a fixed and ice‐following (Lagrangian) reference frame. The heat lost from the upper ocean is large compared with prior observations of ocean heat flux under thick, multi‐year Arctic sea ice. In contrast to prior studies, where almost all heat lost goes into ice melt, a significant portion of the ocean heat released in this event goes directly to the atmosphere, while the remainder (~30–40%) goes into melting sea ice. The magnitude of ocean mixing during this event may have been enhanced by large surface waves, reaching nearly 5 m at the peak, which are becoming increasingly common in the autumn Arctic Ocean. The wave effects are explored by comparing the air‐ice‐ocean evolution observed at short and long fetches, and a common scaling for Langmuir turbulence. After the event, the ocean mixed layer was deeper and cooler, and autumn ice formation resumed.

Observations of surface wave dispersion in the marginal ice zone

Collins, C., M. Doble, B. Lund, and M. Smith, "Observations of surface wave dispersion in the marginal ice zone," J. Geophys. Res., 123, 3336-3354, doi:10.1029/2018JC013788, 2018.

More Info

1 May 2018

This study presents the most comprehensive set of in situ and remote sensing measurements of wave number, and hence the dispersion relation, in ice to date. A number of surface‐following buoys were deployed in sea ice from the R/V Sikuliaq, which also hosted an X‐band marine radar, during the ONR Arctic Sea State field experiment. The heave‐slope‐correlation method was used to estimate the root‐mean‐square wave number from the buoys. The method was highly sensitive to noise, and extensive quality control measures were developed to isolate real signals in the estimated wave number. The buoy measurements were complemented by shipboard marine X‐band radar dispersion measurements, which are limited to lower frequencies (<0.32 Hz). Overall, deviation from the linear open water dispersion relation was not significant, and matched the open water relation nearly exactly for the range 0.10–0.30 Hz. Isolating a subset of data during the strongest wave event showed evidence of increased wave numbers at frequencies greater than 0.30 Hz. The ice conditions and deviation from linear open water dispersion were qualitatively consistent with predictions from the mass loading model. However, the dispersion curves did not exactly follow the contours of the mass loading model, suggesting either measurement error or other processes at play.

Wave attenuation through an arctic marginal ice zone on 12 October 2015. 1. Measurement of wave spectra and ice features from Sentinel 1A

Stopa, J.E., F. Ardhuin, J. Thomson, M.M. Smith, A. Kohout, M. Doble, and P. Wadhams, "Wave attenuation through an arctic marginal ice zone on 12 October 2015. 1. Measurement of wave spectra and ice features from Sentinel 1A," J. Geophys. Res., 123, 3619-3634, doi:10.1029/2018JC013791, 2018.

More Info

1 May 2018

A storm with significant wave heights exceeding 4 m occurred in the Beaufort Sea on 11–13 October 2015. The waves and ice were captured on 12 October by the Synthetic Aperture Radar (SAR) on board Sentinel‐1A, with Interferometric Wide swath images covering 400 x 1,100 km at 10 m resolution. This data set allows the estimation of wave spectra across the marginal ice zone (MIZ) every 5 km, over 400 km of sea ice. Since ice attenuates waves with wavelengths shorter than 50 m in a few kilometers, the longer waves are clearly imaged by SAR in sea ice. Obtaining wave spectra from the image requires a careful estimation of the blurring effect produced by unresolved wavelengths in the azimuthal direction. Using in situ wave buoy measurements as reference, we establish that this azimuth cutoff can be estimated in mixed ocean‐ice conditions. Wave spectra could not be estimated where ice features such as leads contribute to a large fraction of the radar backscatter variance. The resulting wave height map exhibits a steep decay in the first 100 km of ice, with a transition into a weaker decay further away. This unique wave decay pattern transitions where large‐scale ice features such as leads become visible. As in situ ice information is limited, it is not known whether the decay is caused by a difference in ice properties or a wave dissipation mechanism. The implications of the observed wave patterns are discussed in the context of other observations.

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