Assessment of C, N, and Si Isotopes as Tracers of Past Ocean Nutrient and Carbon Cycling

28 pages, 6 figures, 1 box, 1 appendix.-- Data Availability Statement: Data sets presented in this research are available via the following repositories and study (listed by Figure): Figures 3 and 4: (1)δ13CDIC:(a) CLIVAR P16S (Feely et al., 2008) from GLODAPv2.2020 database (Olsen et al., 2020): https://www.glodap.info/index.php/merged-and-adjusted-data-product/. (b) GEOTRACES GA03 (Quay & Wu, 2015) and GP16 (P. Quay, unpublished data) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (2) δ15Nnitrate:(a) CLIVAR P16S (Rafter et al., 2013) from BCO-DMO: https://www.bco-dmo.org/dataset/651722. (b) GEOTRACES GA03 (Marconi et al., 2015) and GP16 (Peters et al., 2018) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (3) δ30Si: GEOTRACES GA03 (Brzezinski & Jones, 2015) and GIPY04 (Fripiat et al., 2012) from GEOTRACES IDP2017 (Schlitzer et al., 2018): https://www.bodc.ac.uk/geotraces/data/idp2017/. (4) Figure 4a POC Flux (DeVries & Weber, 2017): SIMPLE-TRIM Output from https://tdevries.eri.ucsb.edu/models-and-data-products/. Figure 5: (a) Antarctic CO2 composite: https://www.ncdc.noaa.gov/paleo-search/study/17975. (b) ∆δ13Cthermocline-deep from Ziegler et al. (2013) supporting information: https://www.nature.com/articles/ngeo1782; ∆δ13Cepifaunal-infaunal (Hoogakker et al., 2018): https://doi.pangaea.de/10.1594/PANGAEA.891185. (c) SAZ FB-δ15N (Martínez-García et al., 2014): https://www.ncdc.noaa.gov/paleo/study/18318; AZ DB-δ15N (Studer et al., 2015): https://doi.pangaea.de/10.1594/PANGAEA.848271. (d) SAZ Fe flux (Martínez-García et al., 2014): https://www.ncdc.noaa.gov/paleo/study/18318. (e) AZ diatom δ30Si (Robinson et al., 2014): https:// www.ncdc.noaa.gov/paleo/study/17917. Figure 6: (a) and (b) Benthic foraminifera δ18O and δ13C (Zachos et al., 2001): https:// www.ncdc.noaa.gov/paleo/study/8674. (c) FB-δ15N from Kast et al. (2019) supporting information data: https://science.sciencemag.org/content/suppl/2019/04/24/364.6438.386.DC1. (d) and (e) Diatom, sponge, and radiolarian δ30Si in Egan et al. (2013) supporting information: https://www.sciencedirect.com/science/article/pii/S0012821X13002185, Fontorbe et al. (2016) supporting information: https://www.sciencedirect.com/science/article/pii/S0012821X16304265, and Fontorbe et al. (2017) supporting information: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017PA003090Biological productivity in the ocean directly influences the partitioning of carbon between the atmosphere and ocean interior. Through this carbon cycle feedback, changing ocean productivity has long been hypothesized as a key pathway for modulating past atmospheric carbon dioxide levels and hence global climate. Because phytoplankton preferentially assimilate the light isotopes of carbon and the major nutrients nitrate and silicic acid, stable isotopes of carbon (C), nitrogen (N), and silicon (Si) in seawater and marine sediments can inform on ocean carbon and nutrient cycling, and by extension the relationship with biological productivity and global climate. Here, we compile water column C, N, and Si stable isotopes from GEOTRACES-era data in four key ocean regions to review geochemical proxies of oceanic carbon and nutrient cycling based on the C, N, and Si isotopic composition of marine sediments. External sources and sinks as well as internal cycling (including assimilation, particulate matter export, and regeneration) are discussed as likely drivers of observed C, N, and Si isotope distributions in the ocean. The potential for C, N, and Si isotope measurements in sedimentary archives to record aspects of past ocean C and nutrient cycling is evaluated, along with key uncertainties and limitations associated with each proxy. Constraints on ocean C and nutrient cycling during late Quaternary glacial-interglacial cycles and over the Cenozoic are examined. This review highlights opportunities for future research using multielement stable isotope proxy applications and emphasizes the importance of such applications to reconstructing past changes in the oceans and climate systemThis workshop was funded by the United States National Science Foundation (NSF) through the GEOTRACES program, the international Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and NSF, and the French national program LEFE (Les Enveloppes Fluides et l'Environnement). [...] This study was supported by PAGES, LEFE, and GEOTRACES through NSF. J. R. Farmer acknowledges support from the Max Planck Society, the Tuttle Fund of the Department of Geosciences of Princeton University, the Grand Challenges Program of the Princeton Environmental Institute, and through Exxon Mobil via the Andlinger Center for Energy and the Environment of Princeton University. Open access funding enabled and organized by Projekt DEAL. [...] With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

Silicon isotopes highlight the role of glaciated fjords in modifying coastal waters

Glaciers and ice sheets are experiencing rapid warming under current climatic change and there is increasing evidence that glacial meltwaters provide key dissolved and dissolvable amorphous nutrients to downstream ecosystems. However, large debate exists around the fate of these nutrients within complex and heterogenous fjord environments, where biogeochemical cycling is still often poorly understood. We combine silicon (Si) concentration data with isotopic compositions to better understand silicon cycling and export in two contrasting fjordic environments in south-west Greenland. We show that both fjords have isotopically light dissolved silicon (DSi) within surface waters, despite an apparently rapid biological drawdown of DSi with increasing salinity. We hypothesise that such observations cannot be explained by simple water mass mixing processes, and postulate that an isotopically light source of Si, most likely glacially-derived amorphous silica (ASi), is responsible for further modifying these coastal waters within the fjords and beyond. Fjord to coastal exchange is likely a relatively slow process (several months), and thus is less impacted by short-term (< seasonal) changes of glacial meltwater input into the fjord, which has implications when considering the role of glacial meltwaters on nutrient export beyond the shelf break. We highlight the need for isotopic studies combined with dissolved and particulate nutrient concentration analysis to provide a more detailed analysis into the biogeochemical cycles within these highly dynamic fjord environments

Multimessenger astronomy with the Einstein Telescope

Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope. Minor corrections include

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society

Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run

Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow both the frequency and the time derivative of the frequency of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search, we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets. © 2022. The Author(s). Published by the American Astronomical Society

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)

[no abstract available