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Bonnie Light

Principal Physicist

Affiliate Associate Professor, Atmospheric Sciences





Department Affiliation

Polar Science Center


B.S. Engineering, Cornell University, 1986

M.S. Electrical Engineering, University of Maryland - College Park, 1990

M.S. Atmospheric Sciences, University of Washington - Seattle, 1995

Ph.D. Atmospheric Sciences, University of Washington - Seattle, 2000


Earth's Frozen Oceans: Properties and Importance of Sea Ice

Bonnie Light and Maddie Smith present a webinar for the National Ocean Science Bowl (NOSB) Professional Development Program. The NOSB is an academic competition for high school students. This webinar by Light and Smith provides subject matter expertise to NOSB coaches, organizers, and student competitors on the 2021 theme: Plunging Into Our Polar Oceans.

22 Jan 2021

MOSAiC: Multidisciplinary drifting Observatory for the Study of Arctic Climate

Bonnie Light's video tutorial on Sunlight and Arctic Sea Ice, made for the MOSAiC "Frozen in the Ice: Exploring the Arctic" series.

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19 Mar 2020

The goal of the MOSAiC expedition is to take the closest look ever at the Arctic as the epicenter of global warming and to gain insights that are key to understanding global climate change. Hundreds of researchers from 20 countries will work from the icebreaker Polarstern as it is frozen into and drifts with the sea ice for 1 year, 2019–2020. Bonnie Light joins the 5th leg of the expedition during summer 2020 to study the optical properties of melting sea ice.

Extreme Summer Melt: Assessing the Habitability and Physical Structure of Rotting First-year Arctic Sea Ice

Sea ice cover in the Arctic during summer is shrinking and thinning. The melt season is lengthening and the prevalence of "rotten" sea ice is increasing.

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30 Jul 2015

A multidisciplinary team of researchers is making a series of three monthly (May, June, and July) expeditions to Barrow, AK. They are measuring the summertime melt processes that transform the physical properties of sea ice, which in turn transform the biological and chemical properties of the ice habitat.

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2000-present and while at APL-UW

A synthesis of observations and models to assess the time series of sea ice mass balance in the Beaufort Sea

Planck, C.J., D.K. Perovich, and B. Light, "A synthesis of observations and models to assess the time series of sea ice mass balance in the Beaufort Sea," J. Geophys. Res., 125, doi:10.1029/2019JC015833, 2020.

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1 Nov 2020

Over the past four decades, there has been a substantial thinning of the summer sea ice cover in the Beaufort Sea. Variations in sea ice mass balance reflect these changes and give insight to the environmental forcings which caused them. In this work, the time series results from eight Lagrangian mass balance sites that operated in the Beaufort Sea over the years 1997–2015 are analyzed. Direct measurements from the sites are combined with estimates of ice/ocean heat input to examine the roll of solar heating on ice loss, growth, and melt rates. Comparisons between ice and snow conditions and mass balance event timing, for example, surface and bottom melt onset, melt peak, and melt end, are also made. From the late 1990s to the present, a general increase in bottom melting and solar heat input to the upper ocean was observed. All sites showed a net loss of ice (ranging from 29 to 271 cm), and all but one site saw the majority of this loss from bottom melting. Bottom melt onset occurred within a relatively narrow 13‐day window between 1 and 13 June at all sites. The amount of observed bottom melt was also related to the heat deposited in the ocean available for melting, underscoring the increasingly important role of ocean thermodynamics in determining sea ice mass balance.

Physical and optical characteristics of heavily melted 'rotten' Arctic sea ice

Frantz, C.M., B. Light, S.M. Farley, S. Carpenter, R. Lieblappen, Z. Courville, M.V. Orellana, and K. Junge, "Physical and optical characteristics of heavily melted 'rotten' Arctic sea ice," Cryosphere, 13, 775-793, doi:10.5194/tc-13-775-2019, 2019.

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5 Mar 2019

Field investigations of the properties of heavily melted "rotten" Arctic sea ice were carried out on shorefast and drifting ice off the coast of Utqiagvik (formerly Barrow), Alaska, during the melt season. While no formal criteria exist to qualify when ice becomes rotten, the objective of this study was to sample melting ice at the point at which its structural and optical properties are sufficiently advanced beyond the peak of the summer season. Baseline data on the physical (temperature, salinity, density, microstructure) and optical (light scattering) properties of shorefast ice were recorded in May and June 2015. In July of both 2015 and 2017, small boats were used to access drifting rotten ice within ~32 km of Utqiagvik. Measurements showed that pore space increased as ice temperature increased (–8 to 0°C), ice salinity decreased (10 to 0 ppt), and bulk density decreased (0.9 to 0.6 g cm-3). Changes in pore space were characterized with thin-section microphotography and X-ray micro-computed tomography in the laboratory. These analyses yielded changes in average brine inclusion number density (which decreased from 32 to 0.01 mm-3), mean pore size (which increased from 80 μm to 3 mm), and total porosity (increased from 0% to > 45%) and structural anisotropy (variable, with values of generally less than 0.7). Additionally, light-scattering coefficients of the ice increased from approximately 0.06 to > 0.35 cm-1 as the ice melt progressed. Together, these findings indicate that the properties of Arctic sea ice at the end of melt season are significantly distinct from those of often-studied summertime ice. If such rotten ice were to become more prevalent in a warmer Arctic with longer melt seasons, this could have implications for the exchange of fluid and heat at the ocean surface.

Melt pond conditions on declining Arctic sea ice over 1979–2016: Model development, validation, and results

Zhang, J., A. Schwieger, M. Webster, B. Light, M. Steele, C. Ashjian, R. Campbell, and Y. Spitz, "Melt pond conditions on declining Arctic sea ice over 1979–2016: Model development, validation, and results," J. Geophys. Res., 123, 7983-8003, doi:10.1029/2018JC014298, 2018.

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1 Nov 2018

A melt pond (MP) distribution equation has been developed and incorporated into the Marginal Ice‐Zone Modeling and Assimilation System to simulate Arctic MPs and sea ice over 1979–2016. The equation differs from previous MP models and yet benefits from previous studies for MP parameterizations as well as a range of observations for model calibration. Model results show higher magnitude of MP volume per unit ice area and area fraction in most of the Canada Basin and the East Siberian Sea and lower magnitude in the central Arctic. This is consistent with Moderate Resolution Imaging Spectroradiometer observations, evaluated with Measurements of Earth Data for Environmental Analysis (MEDEA) data, and closely related to top ice melt per unit ice area. The model simulates a decrease in the total Arctic sea ice volume and area, owing to a strong increase in bottom and lateral ice melt. The sea ice decline leads to a strong decrease in the total MP volume and area. However, the Arctic‐averaged MP volume per unit ice area and area fraction show weak, statistically insignificant downward trends, which is linked to the fact that MP water drainage per unit ice area is increasing. It is also linked to the fact that MP volume and area decrease relatively faster than ice area. This suggests that overall the actual MP conditions on ice have changed little in the past decades as the ice cover is retreating in response to Arctic warming, thus consistent with the Moderate Resolution Imaging Spectroradiometer observations that show no clear trend in MP area fraction over 2000–2011.

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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