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Bonnie Light

Principal Physicist

Affiliate Associate Professor, Atmospheric Sciences

Email

bonnie@apl.washington.edu

Phone

206-543-9824

Department Affiliation

Polar Science Center

Videos

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.

Investigating Arctic Ice Melt

"Investigating Arctic Ice Melt" is an interactive exhibit at the Pacific Science Center in Seattle, WA. Bonnie Light leads a tour through some of the installations and explains a few of the many pieces to the puzzle: What is causing the decreasing ice up north?

19 Mar 2014

Focus on Arctic Sea Ice: Current and Future States of a Diminished Sea Ice Cover

APL-UW polar scientists are featured in the March edition of the UW TV news magazine UW|360, where they discuss their research on the current and future states of a diminished sea ice cover in the Arctic.

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7 Mar 2012

The dramatic melting of Arctic sea ice over the past several summers has generated great interest and concern in the scientific community and among the public. Here, APL-UW polar scientists present their research on the current state of Arctic sea ice. A long-term, downward trend in sea ice volume is clear.

They also describe how the many observations they gather are used to improve computer simulations of global climate that, in turn, help us to asses the impacts of a future state of diminished sea ice cover in the Arctic.

This movie presentation was first seen on the March 2012 edition of UW|360, the monthly University of Washington Television news magazine.

Publications

2000-present and while at APL-UW

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.

Light availability and phytoplankton growth beneath arctic sea ice: Integrating observations and modeling

Hill, V.J., B. Light, M. Steele, and R.C. Zimmerman, "Light availability and phytoplankton growth beneath arctic sea ice: Integrating observations and modeling," J. Geophys. Res., 123, 3651-3667, doi:10.1029/2017JC013617, 2018.

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1 May 2018

Observations of the seasonal light field in the upper Arctic Ocean are critical to understanding the impacts of changing Arctic ice conditions on phytoplankton growth in the water column. Here we discuss data from a new sensor system, deployed in seasonal ice cover north‐east of Utqiagvik, Alaska in March 2014. The system was designed to provide observations of light and phytoplankton biomass in the water column during the formation of surface melt ponds and the transition from ice to open water. Hourly observations of downwelling irradiance beneath the ice (at 2.9, 6.9, and 17.9 m depths) and phytoplankton biomass (at 2.9 m depth) were transmitted via Iridium satellite from 9 March to 10 November 2014. Evidence of an under‐ice phytoplankton bloom (Chl a ∼8 mg m-3) was seen in June and July. Increases in light intensity observed by the buoy likely resulted from the loss of snow cover and development of surface melt ponds. A bio‐optical model of phytoplankton production supported this probable trigger for the rapid onset of under‐ice phytoplankton growth. Once under‐ice light was no longer a limiting factor for photosynthesis, open water exposure almost marginally increased daily phytoplankton production compared to populations that remained under the adjacent ice. As strong effects of climate change continue to be documented in the Arctic, the insight derived from autonomous buoys will play an increasing role in understanding the dynamics of primary productivity where ice and cloud cover limit the utility of ocean color satellite observations.

The spectral albedo of sea ice and salt crusts on the tropical ocean of Snowball Earth: 1. Laboratory measurements

Light, B., R. Carns, and S.G. Warren, "The spectral albedo of sea ice and salt crusts on the tropical ocean of Snowball Earth: 1. Laboratory measurements," J. Geophys. Res., 121, 4966-4979, doi:10.1002/2016JC011803, 2016.

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16 Jun 2016

The ice-albedo feedback mechanism likely contributed to global glaciation during the Snowball Earth events of the Neoproterozoic era (1 Ga to 544 Ma). This feedback results from the albedo contrast between sea ice and open ocean. Little is known about the optical properties of some of the possible surface types that may have been present, including sea ice that is both snow-free and cold enough for salts to precipitate within brine inclusions. A proxy surface for such ice was grown in a freezer laboratory using the single salt NaCl and kept below the eutectic temperature (–21.2°C) of the NaCl – H2O binary system. The resulting ice cover was composed of ice and precipitated hydrohalite crystals (NaCl ⋅ 2H2O). As the cold ice sublimated, a thin lag-deposit of salt formed on the surface. To hasten its growth in the laboratory, the deposit was augmented by addition of a salt-enriched surface crust. Measurements of the spectral albedo of this surface were carried out over 90 days as the hydrohalite crust thickened due to sublimation of ice, and subsequently over several hours as the crust warmed and dissolved, finally resulting in a surface with puddled liquid brine. The all-wave solar albedo of the subeutectic crust is 0.93 (in contrast to 0.83 for fresh snow and 0.67 for melting bare sea ice). Incorporation of these processes into a climate model of Snowball Earth will result in a positive salt-albedo feedback operating between –21°C and –36°C.

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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