•Ocean tides in at least several cases of the icy satellites are estimated to generate appreciable heat.•Feedbacks may focus ocean configurations in resonantly forced states.•Analyses of the tidal ...dynamics provide indications of why some satellites maintain oceans and others do not.
This study illuminates scenarios whereby the heat produced by the dissipation of ocean tides is significant in the heat budgets maintaining liquid oceans on icy satellites in the outer Solar System. It has been shown in previous work that ocean tides, if resonantly forced, can supply heat at or exceeding the rates necessary for maintaining these oceans. It has also been shown that because of feedbacks these resonant configurations may be unavoidable under typical situations. This study extends from the previous work and seeks to examine the full set of dynamically-consistent ocean tidal solutions to describe the parameter dependencies that may cause one ocean to become trapped in such a vigorous ocean state while allowing another to freeze—why do some of these satellites have oceans, and others do not? It is found that even with no other sources of heat, a liquid ocean on many of these satellites would be maintained by ocean tidal heat because the process of freezing (which changes the thickness of the remaining liquid ocean and thereby the eigenmodes) would push the ocean into a resonant configuration, with the associated increase in heat production preventing further freezing and stabilizing the configuration. An ocean on Io or Mimas would suffer extreme tides (with heat generated exceeding 1W/m2) unless an implausibly large volume of water were present to lift the eigenmodes of the configuration out of resonance with the tidal forces. Europa can maintain a thick (∼100km) ocean due to an obliquity-forced tidal resonance, while parameters for most other satellites suggest eccentricity-driven resonance scenarios involving much thinner ocean thicknesses (1–10skm). But these thin ocean thickness in the latter scenarios will be altered by ice cover: as the ice cover damps the ocean tidal response, significant heat is still generated which would stall freezing but the ocean thicknesses are modified to larger values than would be expected without ice cover.
Previous analyses of hourly tide-gauge data taken at Honolulu since 1905 have shown that both sea level and the amplitude of the tides have increased synchronously over time, and a process has been ...proposed whereby the common cause is an increase in ocean temperature. Validation with independent data of this change in tides, as well as the proposed cause, has been lacking Ocean tides also generate magnetic fields that reach far outside the ocean, and tidal signals are clearly seen in the hourly data since 1905 from the Honolulu geomagnetic observatory. Here, it is found that the tidal amplitudes have increased synchronously in the tide-gauge and magnetic records, providing independent support for the previous results. Further information about the changing ocean is likely contained in the historical data from geomagnetic observatories as well as the global coverage of modern satellite magnetic surveys.
Pulses, including peas, have long been important components of the human diet due to their content of starch, protein and other nutrients. More recently, the health benefits other than nutrition ...associated with pulse consumption have attracted much interest. The focus of the present review paper is the demonstrated and potential health benefits associated with the consumption of peas, Pisum sativum L., specifically green and yellow cotyledon dry peas, also known as smooth peas or field peas. These health benefits derive mainly from the concentration and properties of starch, protein, fibre, vitamins, minerals and phytochemicals in peas. Fibre from the seed coat and the cell walls of the cotyledon contributes to gastrointestinal function and health, and reduces the digestibility of starch in peas. The intermediate amylose content of pea starch also contributes to its lower glycaemic index and reduced starch digestibility. Pea protein, when hydrolysed, may yield peptides with bioactivities, including angiotensin I-converting enzyme inhibitor activity and antioxidant activity. The vitamin and mineral contents of peas may play important roles in the prevention of deficiency-related diseases, specifically those related to deficiencies of Se or folate. Peas contain a variety of phytochemicals once thought of only as antinutritive factors. These include polyphenolics, in coloured seed coat types in particular, which may have antioxidant and anticarcinogenic activity, saponins which may exhibit hypocholesterolaemic and anticarcinogenic activity, and galactose oligosaccharides which may exert beneficial prebiotic effects in the large intestine.
Data from recent space missions have added strong support for the idea that there are liquid oceans on several moons of the outer planets, with Jupiter's moon Europa having received the most ...attention. But given the extremely cold surface temperatures and meagre radiogenic heat sources of these moons, it is still unclear how these oceans remain liquid. The prevailing conjecture is that these oceans are heated by tidal forces that flex the solid moon (rock plus ice) during its eccentric orbit, and that this heat entering the ocean does not rapidly escape because of the insulating layer of ice over the ocean surface. Here, however, I describe strong tidal dissipation (and heating) in the liquid oceans; I show that a subdominant and previously unconsidered tidal force due to obliquity (axial tilt of the moon with respect to its orbital plane) has the right form and frequency to resonantly excite large-amplitude Rossby waves in these oceans. In the specific case of Europa, the minimum kinetic energy of the flow associated with this resonance (7.3 x 10(18) J) is two thousand times larger than that of the flow excited by the dominant tidal forces, and dissipation of this energy seems large enough to be a primary ocean heat source.
This paper provides an analysis of the nature of the Welsh ethnolinguistic community in Blue Earth County, Minnesota, during the late nineteenth and early twentieth centuries. The study considers ...culture maintenance, and suggests that Welsh ethnic integrity was initially maintained due to linguistic necessity, high levels of endogamy, occupational specialization, and the creation of popular cultural institutions. Ultimately, however, the community was undermined, not only by economic change, the cessation of immigration from Wales, and the general forces of acculturation, but also by specifically Welsh factors. The paper suggests, therefore, that while the Welsh experience in Blue Earth County differed sharply from that of the other nationalities of the United Kingdom, it did not simply mirror the experience of other non-Anglophone groups.
Metamorphic proteins switch between different folds, defying the protein folding paradigm. It is unclear how fold switching arises during evolution. With ancestral reconstruction and nuclear magnetic ...resonance, we studied the evolution of the metamorphic human protein XCL1, which has two distinct folds with different functions, making it an unusual member of the chemokine family, whose members generally adopt one conserved fold. XCL1 evolved from an ancestor with the chemokine fold. Evolution of a dimer interface, changes in structural constraints and molecular strain, and alteration of intramolecular protein contacts drove the evolution of metamorphosis. Then, XCL1 likely evolved to preferentially populate the noncanonical fold before reaching its modern-day near-equal population of folds. These discoveries illuminate how one sequence has evolved to encode multiple structures, revealing principles for protein design and engineering.
The electrical conductivity of the ocean is a fundamental parameter in the electrodynamics of the Earth System. This parameter is involved in a number of applications ranging from the calibration of ...in situ ocean flow meters, through extensions of traditional induction studies, and into quite new opportunities involving the remote sensing of ocean flow and properties from space-borne magnetometers such as carried aboard the three satellites of the
Swarm
mission launched in 2013. Here, the first ocean conductivity data set calculated directly from observed temperature and salinity measurements is provided. These data describe the globally gridded, three-dimensional mean conductivity as well as seasonal variations, and the statistics of spatial and seasonal variations are shown. This “climatology” data set of ocean conductivity is offered as a standard reference similar to the ocean temperature and salinity climatologies that have long been available.
Ocean‐generated magnetic field models of the Principal Lunar, M2, and the Larger Lunar elliptic, N2, semidiurnal tidal constituents were estimated through a “Comprehensive Inversion” of the first ...20.5 months of magnetic measurements from European Space Agency's (ESA) Swarm satellite constellation mission. While the constellation provides important north‐south along‐track gradiometry information, it is the unique low‐spacecraft pair that allows for east‐west cross‐track gradiometry. This latter type is crucial in delivering an M2 estimate of similar quality with that derived from over 10 years of CHAMP satellite data but over a shorter interval, at higher altitude, and during more magnetically disturbed conditions. Recovered N2 contains nonoceanic signal but is highly correlated with theoretical models in regions of maximum oceanic amplitude. Thus, satellite magnetic gradiometry may eventually enable the monitoring of ocean electrodynamic properties at temporal resolutions of 1 to 2 years, which may have important implications for the inference of ocean temperature and salinity.
Key Points
Oceanic M2 tidal magnetic signal extracted from only 20.5 months of Swarm data compared to >3.5 years of CHAMP data
Swarm gradiometry allows for extraction from higher‐altitude data compared to CHAMP
Swarm gradiometry allows for extraction during more magnetically disturbed times compared to CHAMP
ABSTRACT Active volcanism observed on Io is thought to be driven by the temporally periodic, spatially differential projection of Jupiter's gravitational field over the moon. Previous theoretical ...estimates of the tidal heat have all treated Io as essentially a solid, with fluids addressed only through adjustment of rheological parameters rather than through appropriate extension of the dynamics. These previous estimates of the tidal response and associated heat generation on Io are therefore incomplete and possibly erroneous because dynamical aspects of the fluid behavior are not permitted in the modeling approach. Here we address this by modeling the partial-melt asthenosphere as a global layer of fluid governed by the Laplace Tidal Equations. Solutions for the tidal response are then compared with solutions obtained following the traditional solid-material approach. It is found that the tidal heat in the solid can match that of the average observed heat flux (nominally 2.25 W m−2), though only over a very restricted range of plausible parameters, and that the distribution of the solid tidal heat flux cannot readily explain a longitudinal shift in the observed (inferred) low-latitude heat fluxes. The tidal heat in the fluid reaches that observed over a wider range of plausible parameters, and can also readily provide the longitudinal offset. Finally, expected feedbacks and coupling between the solid/fluid tides are discussed. Most broadly, the results suggest that both solid and fluid tidal-response estimates must be considered in exoplanet studies, particularly where orbital migration under tidal dissipation is addressed.
Abstract
To overcome challenges with observing ocean heat content (OHC) over the entire ocean, we propose a novel approach that exploits the abundance of satellite data, including data from modern ...satellite geomagnetic surveys such as Swarm. The method considers a novel combination of conventional in situ (temperature and pressure) as well as satellite (altimetry and gravimetry) data with estimates of ocean electrical conductance (depth-integrated conductivity), which can potentially be obtained from magnetic observations (by satellite, land, seafloor, ocean, and airborne magnetometers). To demonstrate the potential benefit of the proposed method, we sample model output of an ocean state estimate to reflect existing observations and train a machine learning algorithm Generalized Additive Model (GAM) on these samples. We then calculate OHC everywhere using information potentially derivable from various global satellite coverage—including magnetic observations—to gauge the GAM’s goodness of fit on a global scale. Inclusion of in situ observations of OHC in the upper 2000 m from Argo-like floats and conductance data each reduce the root-mean-square error by an order of magnitude. Retraining the GAM with recent ship-based hydrographic data attains a smaller RMSE in polar oceans than training the GAM only once on all available historical ship-based hydrographic data; the opposite is true elsewhere. The GAM more accurately calculates OHC anomalies throughout the water column than below 2000 m and can detect global OHC anomalies over multiyear time scales, even when considering hypothetical measurement errors. Our method could complement existing methods and its accuracy could be improved through careful ship-based campaign planning.
Significance Statement
The purpose of this manuscript is to demonstrate the potential for practical implementation of a remote monitoring method for ocean heat content (OHC) anomalies. To do this, we sample data from a reanalysis product primarily because of the dearth of observations below 2000 m depth that can be used for validation and the fact that full-depth-integrated electrical seawater conductivity data products derived from satellite magnetometry are not yet available. We evaluate multiple factors related to the accuracy of OHC anomaly estimation and find that, even with hypothetical measurement errors, our method can be used to monitor OHC anomalies on multiyear time scales.
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