By the end of this century, the Oceans will markedly change in response to anthropogenic stressors and increasing greenhouse gas emissions. Their circulation and the horizontal and vertical transport of heat, salt, carbon, oxygen and nutrients will be impacted. In response to rising temperatures, stratification will increase in the upper water column, affecting ventilation of the deep ocean and nutrient transport from the deep and nutrient-rich waters to the euphotic layer.
Phosphorus (P) is an essential and limited micronutrient regulating marine primary productivity. Despite the critical roles of marine P cycle in global biogeochemical processes, the mechanisms leading to marine P removal as authigenic apatite are not fully understood. This dissertation investigates the mineralogical and geochemical controls on marine polyphosphate (polyP) transformation and mineralization under laboratory controlled experiments and sediment incubations.
We present a systematic modeling framework for the identification of water vapor plumes in plasma and magnetic field data from spacecraft flybys of Jupiter's moon Europa. In particular, we determine the degree to which different plume configurations can be obscured by the interaction of Jupiter's magnetospheric plasma with Europa's induced dipole field and its global atmosphere. Additionally we constrain the diagnostic potential of ion energy spectrograms to identify signatures of water vapor plumes in the thermal plasma environment of Europa.
Pacific climate and weather extreme events such as heatwaves, drought, and hydrological extremes are dynamically linked large-scale climate variability. This work aims at improving the current understanding of the role of climate coupling within the Pacific system and investigating their changes to anthropogenic forcing.
Particulate matter (PM) is an important component of the atmosphere which affects the planetary energy budget, visibility, and public health. Although atmospheric PM is a complex mixture of inorganic and organic components from a variety of sources, organic aerosols (OA) represent a significant fraction (20-90%) of tropospheric submicron PM. A better understanding of atmospheric organic aerosols is essential to evaluate their impact and develop effective regulations.
Dissolved oxygen (DO) is essential for marine life and biogeochemical cycling. To a first order, DO is determined by the competition between ocean ventilation and biological productivity. Approximately 21% of the atmospheric gases is oxygen, and the waters at the ocean surface are enriched in DO. Ventilation occurs through a suite of physical processes that brings the DO-rich surface waters into the interior ocean.
Ground-level ozone is a secondary atmospheric pollutant that damages human and vegetation health. The chemical production of ground-level ozone involves the photochemical reactions between nitrogen oxides (NOX = NO + NO2) and volatile organic compounds (VOCs). China is experiencing high levels of ozone due to high precursor emissions in association with rapid urbanization and industrialization in past decades.
The transport of biomass burning aerosols and the oxidation state of the marine boundary layer (MBL) play significant roles in understanding the background climate condition of the remote regions. Biomass burning is provoked by natural factors or humans and has a profound impact on ecosystems, carbon cycles, climate change, and human society. Biomass burning is one major source of atmospheric aerosols, which is a potential medium in fire-climate interactions because of its role in the global radiative balance and cloud processing.
In this thesis, I adopt ideas of finding the structure from randomness to recover the low-rank representations of the full subsurface extended image volumes which can give us access to any elements and image gathers. I derived the time-domain wave-equation based factorization via randomly probing which helps to remove the computational bottlenecks in both wave-equation solves and the imaging conditions. Also, I designed the framework combined with power iterations to increase the recovered accuracy without increasing the probing size.