81 research outputs found
Vertical mixing alleviates autumnal oxygen deficiency in the central North Sea
There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O2) concentrations. Here we use high-resolution glider observations of turbulence and O2 concentrations to directly estimate the vertical O2 flux into the bottom mixed layer (BML) immediately before the autumn breakdown of stratification in a seasonally stratified shelf sea. We present a novel method to resolve the oxycline across sharp gradients due to slow optode response time and optode positioning in a flow âshadow zoneâ on Slocum gliders. The vertical O2 flux to the low-O2 BML was found to be between 2.5 to 6.4 mmol mâ2 dâ1. Episodic intense mixing events were responsible for the majority (up to 90 %) of this oxygen supply despite making up 40 % of the observations. Without these intense mixing events, BML O2 concentrations would approach ecologically concerning levels by the end of the stratified period. Understanding the driving forces behind episodic mixing and how these may change under future climate scenarios and renewable energy infrastructure is key for monitoring shelf sea health
Application of a new net primary production methodology: a daily to annual-scale data set for the North Sea, derived from autonomous underwater gliders and satellite Earth observation
Shelf seas play a key role in both the global carbon cycle and coastal marine ecosystems through the
draw-down and fixing of carbon, as measured through phytoplankton net primary production (NPP). Measuring
NPP in situ and extrapolating this to the local, regional, and global scale presents challenges however because of
limitations with the techniques utilised (e.g. radiocarbon isotopes), data sparsity, and the inherent biogeochemical
heterogeneity of coastal and open-shelf waters.
Here, we introduce a new data set generated using a technique based on the synergistic use of in situ glider
profiles and satellite Earth observation measurements which can be implemented in a real-time or delayedïżœmode system (https://doi.org/10.5285/e6974644-2026-0f94-e053-6c86abc00109; Loveday and Smyth, 2022).
We apply this system to a fleet of gliders successively deployed over a 19-month time frame in the North Sea,
generating an unprecedented fine-scale time series of NPP in the region. At a large scale, this time series gives
close agreement with existing satellite-based estimates of NPP for the region and previous in situ estimates.
What has not been elucidated before is the high-frequency, small-scale, depth-resolved variability associated
with bloom phenology, mesoscale phenomena, and mixed layer dynamics
Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime
Projected sensitivity of the LUX-ZEPLIN experiment to the two-neutrino and neutrinoless double beta decays of Xe-134
Projected sensitivities of the LUX-ZEPLIN experiment to new physics via low-energy electron recoils
LUX-ZEPLIN is a dark matter detector expected to obtain world-leading sensitivity to weakly-interacting massive particles interacting via nuclear recoils with a
âŒ
7
-tonne xenon target mass. This paper presents sensitivity projections to several low-energy signals of the complementary electron recoil signal type: 1) an effective neutrino magnetic moment, and 2) an effective neutrino millicharge, both for
p
p
-chain solar neutrinos, 3) an axion flux generated by the Sun, 4) axionlike particles forming the Galactic dark matter, 5) hidden photons, 6) mirror dark matter, and 7) leptophilic dark matter. World-leading sensitivities are expected in each case, a result of the large 5.6 t 1000 d exposure and low expected rate of electron-recoil backgrounds in the
<
100
â
â
keV
energy regime. A consistent signal generation, background model and profile-likelihood analysis framework is used throughout
Constitutive parameters for earthquake rupture dynamics based on high-velocity friction tests with variable sliprate
The LUX-ZEPLIN (LZ) radioactivity and cleanliness control programs
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4Ă10â48cm2 for a WIMP mass of 40GeV/c2 and a 1000days exposure. LZ achieves this sensitivity through a combination of a large 5.6t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented
A next-generation liquid xenon observatory for dark matter and neutrino physics
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector
Projected sensitivities of the LUX-ZEPLIN (LZ) experiment to new physics via low-energy electron recoils
Projected sensitivity of the LUX-ZEPLIN (LZ) experiment to the two-neutrino and neutrinoless double beta decays of 134Xe
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