Development of Decision Support Systems for Estimating Salinity Instrusion Effects due to Climate Change on the South Carolina and Georgia Coast

2010 S.C. Water Resources Conference - Science and Policy Challenges for a Sustainable Futur

Derivation of tropospheric methane from TCCON CH₄ and HF total column observations

The Total Carbon Column Observing Network (TCCON) is a global ground-based network of Fourier transform spectrometers that produce precise measurements of column-averaged dry-air mole fractions of atmospheric methane (CH₄). Temporal variability in the total column of CH₄ due to stratospheric dynamics obscures fluctuations and trends driven by tropospheric transport and local surface fluxes that are critical for understanding CH₄ sources and sinks. We reduce the contribution of stratospheric variability from the total column average by subtracting an estimate of the stratospheric CH₄ derived from simultaneous measurements of hydrogen fluoride (HF). HF provides a proxy for stratospheric CH₄ because it is strongly correlated to CH₄ in the stratosphere, has an accurately known tropospheric abundance (of zero), and is measured at most TCCON stations. The stratospheric partial column of CH₄ is calculated as a function of the zonal and annual trends in the relationship between CH₄ and HF in the stratosphere, which we determine from ACE-FTS satellite data. We also explicitly take into account the CH₄ column averaging kernel to estimate the contribution of stratospheric CH₄ to the total column. The resulting tropospheric CH₄ columns are consistent with in situ aircraft measurements and augment existing observations in the troposphere

Reinforcing the North Atlantic backbone: revision and extension of the composite splice at ODP Site 982

Ocean Drilling Program (ODP) Site 982 represents a key location for understanding the evolution of climate in the North Atlantic over the past 12Ma. However, concerns exist about the validity and robustness of the underlying stratigraphy and astrochronology, which currently limits the adequacy of this site for high-resolution climate studies. To resolve this uncertainty, we verify and extend the early Pliocene to late Miocene shipboard composite splice at Site 982 using high-resolution XRF core scanning data and establish a robust high-resolution benthic foraminiferal stable isotope stratigraphy and astrochronology between 8.0 and 4.5Ma. Splice revisions and verifications resulted in  ∼ 11m of gaps in the original Site 982 isotope stratigraphy, which were filled with 263 new isotope analyses. This new stratigraphy reveals previously unseen benthic δ18O excursions, particularly prior to 6.65Ma. The benthic δ18O record displays distinct, asymmetric cycles between 7.7 and 6.65Ma, confirming that high-latitude climate is a prevalent forcing during this interval. An intensification of the 41kyr beat in both the benthic δ13C and δ18O is also observed  ∼ 6.4Ma, marking a strengthening in the cryosphere–carbon cycle coupling. A large  ∼ 0.7‰ double excursion is revealed  ∼ 6.4–6.3Ma, which also marks the onset of an interval of average higher δ18O and large precession and obliquity-dominated δ18O excursions between 6.4 and 5.4Ma, coincident with the culmination of the late Miocene cooling. The two largest benthic δ18O excursions  ∼ 6.4–6.3Ma and TG20/22 coincide with the coolest alkenone-derived sea surface temperature (SST) estimates from Site 982, suggesting a strong connection between the late Miocene global cooling, and deep-sea cooling and dynamic ice sheet expansion. The splice revisions and revised astrochronology resolve key stratigraphic issues that have hampered correlation between Site 982, the equatorial Atlantic and the Mediterranean. Comparisons of the revised Site 982 stratigraphy to high-resolution astronomically tuned benthic δ18O stratigraphies from ODP Site 926 (equatorial Atlantic) and Ain el Beida (north-western Morocco) show that prior inconsistencies in short-term excursions are now resolved. The identification of key new cycles at Site 982 further highlights the requirement for the current scheme for late Miocene marine isotope stages to be redefined. Our new integrated deep-sea benthic stable isotope stratigraphy and astrochronology from Site 982 will facilitate future high-resolution late Miocene to early Pliocene climate research

Tetraspanins in zebrafish development

Introduction: Tetraspanins represent a family of integral membrane proteins involved in cell-cell interaction, including adhesion, fusion, differentiation and proliferation. These basic functions are essential for embryonic development, yet there is little research on the role of tetraspanins in this process. The aim of my project is to pilot zebrafish as a new and sensitive model for assessing tetraspanin function in vertebrate development. Background: There are approximately 50 tetraspanin genes in zebrafish, representing orthologues of most of the 33 mammalian genes. mRNA expression analysis has shown that at least 22 of these are expressed in zebrafish embryos and thus may regulate developmental processes. CD9 is a well-characterized tetraspanin and we have shown that zebrafish CD9 orthologues are present in the posterior lateral line (pLL), a sensory system comprised of hair-cell containing neuromasts. The development of the pLL coordinates proliferation, deposition and migration simultaneously and thus requires highly regulated cell interactions. Major findings: We generated CRISPR double knockouts (dKOs) of both zebrafish CD9 paralogues. The dKOs are adult viable and fertile, in contrast to mouse CD9 KO females which are sterile. Inspection of the pLL in the CD9 KOs revealed that there is measurably slower migration of the primordium and fewer hair cells in the posterior neuromasts at 10 dpf. Furthermore we observed a reduced regenerative capacity of the dKO neuromasts, and also upregulation of CD9 paralogues during bone repair. Conclusions: Our results suggest a role for CD9 in collective cell migration and hair cell development. We will analyse the organisation and migration of the primordium in more detail as well as the development and regeneration of the neuromasts and bone. This will be aided by generating fluorescent transgenic zebrafish to visualise dynamic processes involved. This offers a unique insight into the in vivo function of tetraspanins

Intercomparability of X_(CO_2) and X_(CH_4) from the United States TCCON sites

The Total Carbon Column Observing Network (TCCON) has become the standard for long-term column-averaged measurements of CO_2 and CH_4. Here, we use a pair of portable spectrometers to test for intra-network bias among the four currently operating TCCON sites in the United States (US). A previous analytical error analysis has suggested that the maximum 2σ site-to-site relative (absolute) bias of TCCON should be less than 0.2% (0.8ppm) in X_(CO_2) and 0.4% (7ppb) in X_(CH_4). We find here experimentally that the 95% confidence intervals for maximum pairwise site-to-site bias among the four US TCCON sites are 0.05–0.14% for X_(CO_2) and 0.08–0.24% for X_(CH_4). This is close to the limit of the bias we can detect using this methodology

Methane emissions from dairies in the Los Angeles Basin

We estimate the amount of methane (CH_4) emitted by the largest dairies in the southern California region by combining measurements from four mobile solar-viewing ground-based spectrometers (EM27/SUN), in situ isotopic ^(13∕12)CH_4 measurements from a CRDS analyzer (Picarro), and a high-resolution atmospheric transport simulation with a Weather Research and Forecasting model in large-eddy simulation mode (WRF-LES). The remote sensing spectrometers measure the total column-averaged dry-air mole fractions of CH_4 and CO_2 (X_(CH)_4 and X_(CO)_2) in the near infrared region, providing information on total emissions of the dairies at Chino. Differences measured between the four EM27/SUN ranged from 0.2 to 22 ppb (part per billion) and from 0.7 to 3 ppm (part per million) for X_(CH)_4 and X_(CO)_2, respectively. To assess the fluxes of the dairies, these differential measurements are used in conjunction with the local atmospheric dynamics from wind measurements at two local airports and from the WRF-LES simulations at 111 m resolution. Our top-down CH_4 emissions derived using the Fourier transform spectrometers (FTS) observations of 1.4 to 4.8 ppt s^(−1) are in the low end of previous top-down estimates, consistent with reductions of the dairy farms and urbanization in the domain. However, the wide range of inferred fluxes points to the challenges posed by the heterogeneity of the sources and meteorology. Inverse modeling from WRF-LES is utilized to resolve the spatial distribution of CH_4 emissions in the domain. Both the model and the measurements indicate heterogeneous emissions, with contributions from anthropogenic and biogenic sources at Chino. A Bayesian inversion and a Monte Carlo approach are used to provide the CH_4 emissions of 2.2 to 3.5 ppt s^(−1) at Chino

Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity

Within the California South Coast Air Basin (SoCAB), X_(CO)_2 varies significantly due to atmospheric dynamics and the nonuniform distribution of sources. X_(CO)_2 measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin-background differences that are in close agreement for three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory-2 (OCO-2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1σ). We further observe persistent significant differences (∼0.9 ppm) in X_(CO)_2 between two TCCON sites located only 9 km apart within the SoCAB. We estimate that 20% (±1σ confidence interval (CI): 0%, 58%) of the variance is explained by a difference in elevation using a full physics and emissions model and 36% (±1σ CI: 10%, 101%) using a simple, fixed mixed layer model. This effect arises in the presence of a sharp gradient in any species (here we focus on CO_2) between the mixed layer (ML) and free troposphere. Column differences between nearby locations arise when the change in elevation is greater than the change in ML height. This affects the fraction of atmosphere that is in the ML above each site. We show that such topographic effects produce significant variation in X_(CO)_2 across the SoCAB as well