The strength of mixing in the Arctic Ocean is an important control on the ability of heat in the ocean interior to penetrate the stratified upper ocean below the sea ice (D'Asaro & Morison, 1992). However, our understanding of mixing in the Arctic Ocean is arguably the most limited of all regions of the world ocean. As a consequence, the spatiotemporal variability of heat loss from inflowing Atlantic and Pacific waters is not well known (e.g., Lenn et al., 2009;Lincoln et al., 2016). In particular, observations of mixing in the Arctic Ocean are scarce, with direct (i.e., microstructure) inferences of ocean mixing being limited both temporally and geographically. In large-scale studies of ocean mixing rates inferred using indirect methods (
Our understanding of ocean mixing is challenged by its patchy, episodic nature and a scarcity of direct measurements, especially in the Arctic Ocean. In this study, we exploit a historical record of nearly 3,000 conductivity‐temperature‐depth profiles collected in the shelf and shelf‐slope waters of the Canadian Arctic Ocean from 2002 to 2016 to characterize the variability of 28,872 internal wave‐driven turbulent dissipation and mixing rate estimates from a finescale parameterization. We find that these estimates of wave‐driven dissipation rates and associated diapycnal diffusivities are generally low, but exhibit wide variability, each spanning several orders of magnitude. We further find that stratification plays a significant role in modulating the mixing rate both vertically and regionally within the study domain. Dissipation rate and diffusivity estimates display a weak seasonal cycle, but no evidence of statistically significant interannual trends over this period. Exceptionally large localized temporal variability appears to dominate other potential underlying patterns. The presence of strong upper ocean stratification combined with predominately weak dissipation rate estimates implies that many regions in the Canadian Arctic Ocean are likely in a molecular or buoyancy‐controlled mixing regime. Even when the concept of a turbulent‐enhanced diffusivity is potentially relevant, most turbulent heat flux estimates out of the Atlantic Water thermocline are smaller than the average value required to close the standardly assumed Arctic Ocean heat budget. In contrast, we find evidence for isolated occurrences of anomalously large heat fluxes, which may disproportionately contribute to the liberation of Atlantic Water heat toward the surface sea ice pack.
In recent work we constructed completely general conservation laws for energy [1] and linear and angular momentum [2] of extended systems in general relativity based on the notion of a rigid quasilocal frame (RQF). We argued at a fundamental level that these RQF conservation laws are superior to conservation laws based on the local stress-energy-momentum tensor of matter because (1) they do not rely on spacetime symmetries and (2) they properly account for both matter and gravitational effects. Moreover, they provide simple, exact, operational expressions for fluxes of gravitational energy and linear and angular momentum. In this paper we derive the form of these laws in a general first post-Newtonian (1PN) approximation, and then apply these approximate laws to the problem of gravitational tidal interactions. We obtain formulas for tidal heating and tidal torque that agree with the literature, but without resorting to the use of pseudotensors. We describe the physical mechanism of these tidal interactions not in the traditional terms of a Newtonian gravitational force, but in terms of a much simpler and universal mechanism that is an exact, quasilocal manifestation of the equivalence principle in general relativity. As concrete examples, we look at the tidal heating of Jupiter's moon Io and angular momentum transfer in the Earth-Moon system that causes a gradual spin-down of the Earth and recession of the Moon. In both examples we find agreement with observation. arXiv:1312.3617v2 [gr-qc]
We complete the analysis of part I in this series [S. Stotyn et. al.,Phys. Rev. D 89, 044017 (2014)] by numerically constructing boson stars in 2 þ 1 dimensional Einstein gravity with negative cosmological constant, minimally coupled to a complex scalar field. These lower dimensional boson stars have strikingly different properties than their higher dimensional counterparts, most noticeably that there exists a finite central energy density, above which an extremal Bañados-Teitelboim-Zanelli (BTZ) black hole forms. In this limit, all of the scalar field becomes enclosed by the horizon; it does not contract to a singularity, but rather the origin remains smooth and regular and the solution represents a spinning boson star trapped inside a degenerate horizon. Additionally, whereas in higher dimensions the mass, angular momentum, and angular velocity all display damped harmonic oscillations as functions of the central energy density, in D ¼ 3 these quantities change monotonically up to the bound on the central energy density. Some implications for the holographic dual of these objects are discussed and it is argued that the boson star and extremal BTZ black hole phases are dual to a spontaneous symmetry breaking at zero temperature but finite energy scale.
This work investigates how internal wave-driven turbulence varies in time, from hourly to yearly timescales, and in space, across two distinct regions of the Arctic Ocean. We apply a shear-based fine-scale parameterization to mooring records in Nares Strait and on the Beaufort Sea shelf-slope that sampled the upper stratified water column every 30-45 min and span 2003-2006 and 2003-2004, respectively. In doing so, we generate over 600,000 estimates of the internal wave-driven dissipation rate. These estimates exhibit large temporal variability in both regions, spanning over 3 orders of magnitude. Despite these wide ranges, we find distinct distributions at each site. In Nares Strait, the time series of dissipation shows systematic variation at tidal frequencies, and tidal forcing appears to influence dissipation more strongly than winds, sea ice, and stratification on daily timescales. On longer timescales, dissipation exhibits a weak seasonal cycle, being elevated when the stratification is high and during the ice melt season. In the Beaufort Sea, we detect no dominant timescales or significant relationships with forcing metrics, but note that the dissipation rate is typically 2 orders of magnitude lower than that in Nares Strait. This region is characterized as being in a turbulent mixing regime for only 2% of the record, compared to 73% of the Nares Strait record, implying that turbulence here is rarely energetic enough relative to the stratification to drive a turbulent heat flux. Inferred Beaufort Sea heat fluxes are an order of magnitude lower than the O(1) W m −2 average value found in Nares Strait. Plain Language Summary Arctic Ocean mixing rates and how they vary in space and time have important consequences for the transport of heat, salt, and nutrients. However, the tasks of understanding how mixing changes water properties and of predicting future changes to Arctic Ocean mixing rates remain challenging, particularly given that most observations used to study mixing in the Arctic Ocean to date are geographically and temporally limited. In this study, we infer mixing rates by using an estimation technique that relates ocean turbulence to properties of internal waves in the ocean interior. We apply this technique to highly resolved, multiyear measurements obtained from two distinct regions of the Arctic Ocean. Using these estimates, we characterize the statistical distributions of mixing metrics and find strong regional differences between the two study sites. We find that one region is highly energetic and displays systematic patterns in mixing intensity at tidal and seasonal timescales. Turbulent energy at the other site is 2 orders of magnitude weaker, and active turbulent mixing occurs extremely infrequently. These results help to put previous mixing observations into a more informed context and provide insight into the underlying causes of Arctic Ocean mixing patterns.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.