Publications by authors named "Thomas C J Hill"
Article Synopsis
- Ice-nucleating particles (INPs) are key aerosols in the atmosphere that trigger ice formation, but predicting their concentrations in climate models is difficult.
- Researchers developed a method to differentiate INP sources from dust, sea spray aerosol (SSA), and bioaerosol, using data from Bodega Bay, California.
- Findings showed that bioaerosols were the main contributor to INPs at certain temperatures, while current models accurately reflected dust and SSA INP levels but struggled with bioaerosols, indicating the need for further study on their emission and efficiency.
Permafrost underlies approximately a quarter of the Northern Hemisphere and is changing amidst a warming climate. Thawed permafrost can enter water bodies through top-down thaw, thermokarst erosion, and slumping. Recent work revealed that permafrost contains ice-nucleating particles (INPs) with concentrations comparable to midlatitude topsoil.
View Article and Find Full Text PDFThe Arctic is warming faster than anywhere else on Earth, prompting glacial melt, permafrost thaw, and sea ice decline. These severe consequences induce feedbacks that contribute to amplified warming, affecting weather and climate globally. Aerosols and clouds play a critical role in regulating radiation reaching the Arctic surface.
View Article and Find Full Text PDFIce nucleating particles (INPs) influence weather and climate by their effect on cloud phase state. Fatty alcohols present within aerosol particles confer a potentially important source of ice nucleation activity to sea spray aerosol produced in oceanic regions. However, their interactions with other aerosol components and the influence on freezing were previously largely unknown.
View Article and Find Full Text PDFBlack carbon (BC) aerosol plays an important role in the Earth's climate system because it absorbs solar radiation and therefore potentially warms the climate; however, BC can also act as a seed for cloud particles, which may offset much of its warming potential. If BC acts as an ice nucleating particle (INP), BC could affect the lifetime, albedo, and radiative properties of clouds containing both supercooled liquid water droplets and ice particles (mixed-phase clouds). Over 40% of global BC emissions are from biomass burning; however, the ability of biomass burning BC to act as an INP in mixed-phase cloud conditions is almost entirely unconstrained.
View Article and Find Full Text PDFAirborne bacteria confirm the pristine nature of the Southern Ocean boundary layer.
Proc Natl Acad Sci U S A
June 2020
Microorganisms are ubiquitous and highly diverse in the atmosphere. Despite the potential impacts of airborne bacteria found in the lower atmosphere over the Southern Ocean (SO) on the ecology of Antarctica and on marine cloud phase, no previous region-wide assessment of bioaerosols over the SO has been reported. We conducted bacterial profiling of boundary layer shipboard aerosol samples obtained during an Austral summer research voyage, spanning 42.
View Article and Find Full Text PDFArticle Synopsis
- The study examined airborne bacterial communities in Tokyo, analyzing their dynamics in relation to local meteorological conditions and the long-range transport of microbes.
- Samples were collected over 48 to 72 hours and analyzed for microbial diversity using next generation sequencing, showing that while source regions shifted from oceanic to continental origins, the community composition remained stable.
- Findings indicated that local factors like relative humidity and wind speed significantly impacted microbial diversity, with soil and bay seawater identified as major local sources, particularly influenced by humidity and soil moisture levels.
Heterogeneous ice nucleation in the atmosphere regulates cloud properties, such as phase (ice versus liquid) and lifetime. Aerosol particles of marine origin are relevant ice nucleating particle sources when marine aerosol layers are lifted over mountainous terrain and in higher latitude ocean boundary layers, distant from terrestrial aerosol sources. Among many particle compositions associated with ice nucleation by sea spray aerosols are highly saturated fatty acids.
View Article and Find Full Text PDFTerrestrial Origin for Abundant Riverine Nanoscale Ice-Nucleating Particles.
Environ Sci Technol
November 2018
Ice-nucleating particles (INPs) associated with fresh waters are a neglected, but integral component of the water cycle. Abundant INPs were identified from surface waters of both the Maumee River and Lake Erie with ice nucleus spectra spanning a temperature range from -3 to -15 °C. The majority of river INPs were submicron in size and attributed to biogenic macromolecules, inferred from the denaturation of ice-nucleation activity by heat.
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- Sea spray aerosol (SSA) particles significantly affect climate by scattering solar radiation and aiding in cloud formation, with their composition influenced by oceanic biological processes, especially during phytoplankton blooms.
- A mesocosm study using natural seawater revealed that two distinct phytoplankton blooms led to different SSA chemical compositions; the first bloom produced organic-rich SSA, while the second did not.
- The research highlights the complexity of SSA composition influence, showing that it is governed not only by phytoplankton abundance (measured by chlorophyll-a) but also by microbial degradation processes affecting the organic material produced during these blooms.
Ice nucleating particles (INPs) are vital for ice initiation in, and precipitation from, mixed-phase clouds. A source of INPs from oceans within sea spray aerosol (SSA) emissions has been suggested in previous studies but remained unconfirmed. Here, we show that INPs are emitted using real wave breaking in a laboratory flume to produce SSA.
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- - The study investigates the role of ice nucleation-active (INA) bacteria in cloud processes and how they may influence glaciation and precipitation, highlighting uncertainty in their environmental impact.
- - Two quantitative PCR tests were developed to measure the abundance of INA bacteria in environmental samples, successfully identifying new bacterial clades related to well-known species like Pseudomonas and Pantoea.
- - Results showed high concentrations of ina genes in cultivated crops but lower amounts in natural vegetation; however, a biological source was found to be a major contributor to ice-nucleating particles in fresh snow, while a thunderstorm hail sample indicated a significant presence of INA bacteria.