Thomas Peacock

Abstract Near-bottom currents collected over 1 year (August 2021–22) using a current- and pressure-recording inverted echo sounder (CPIES) at a depth of 1060 m showed fluctuations within a frequency band between 2 and 6.5 days near the southwestern slope of the Chukchi Abyssal Plain. The amplitude of the fluctuations was approximately 8 cm s −1 on average during the summer months and weakened to approximately 3 cm s −1 between February and June 2022. Similar fluctuations were reproduced by the data-assimilated Hybrid Coordinate Ocean Model (HYCOM), confirming that they were bottom intensified. Calculations of the bottom-trapping scale using HYCOM revealed that these fluctuations could be attributed to topographic Rossby waves (TRWs) with a length scale of approximately 50 km. The spatial distributions of TRWs in HYCOM and ray-tracing results suggest that TRWs likely propagated from the west-southwest. It is suggested that these TRWs were triggered by nonlocal wind stress curl (WSC), 220 km to the west along the continental slope, as the coherence in the TRW frequency band between the TRWs and WSC was significant. The weaker TRW signal from February to June 2022 was related to weaker WSC and higher sea ice concentration in the study area. The stronger TRWs from July to October occurred when the WSC was stronger and the sea ice concentration was lower in the study area. Our findings imply that changes in the Arctic WSC field or a longer sea ice–free season could trigger more energetic and frequent TRWs, observable down to 1000-m depth around the southwestern slope of the Chukchi Abyssal Plain.

BACKGROUND: Transforaminal lumbar interbody fusion (TLIF) and lateral approaches such as lateral lumbar interbody fusion (LLIF) are widely used to treat degenerative lumbar disk disease. Although both restore disk height and achieve fusion, comparative advantages in radiographic, perioperative, and patient-reported outcomes (PROs) remain debated. PURPOSE: To perform an updated meta-analysis comparing TLIF and LLIF with respect to perioperative outcomes, radiographic parameters, complication rates, and PROs. STUDY DESIGN: Systematic review and meta-analysis. METHODS: A comprehensive search of PubMed, Cochrane, and Google Scholar (2000 to 2025) was conducted per Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies directly comparing TLIF and LLIF were included. Random-effects models were used for pooled analyses. Radiographic outcomes were grouped into immediate and 1- to 2-year follow-up. PROs were stratified by early (≤6 months) and late (>6 months) follow-up. RESULTS: Twenty-seven studies (6,047 patients) met inclusion criteria: 4,098 underwent TLIF and 1,949 underwent LLIF. LLIF was associated with shorter surgical time (-14.3 minute; P = 0.04), lower estimated blood loss (-88.3 mL; P < 0.0001), and reduced length of stay (-0.35 days; P = 0.01). LLIF showed greater immediate improvements in mean disk height (+1.68 mm; P = 0.006), foraminal height (+1.80 mm; P < 0.0001), and segmental lordosis (+2.16°; P = 0.03), with lower subsidence risk (odds ratio: 0.40; P = 0.004). TLIF achieved greater immediate canal decompression (+49.8 mm 2 ; P < 0.0001). At late follow-up, LLIF maintained superior disk height (+2.21 mm), foraminal height (+2.33 mm), and segmental lordosis (+3.01°). LLIF was also associated with improved late leg pain scores (Δ -0.23; P = 0.02). CONCLUSION: LLIF and TLIF each offer distinct advantages. LLIF was associated with lower subsidence risk, reduced blood loss, shorter surgical time, decreased length of stay, and improved radiographic correction. Most PROs were comparable, but TLIF demonstrated improved late leg pain relief. LEVEL OF EVIDENCE: III.

Abstract Deep-sea polymetallic nodule mining is in the exploration phase at present with some groups proposing a move towards extraction within years 1 . Management of this industry requires evidence of the long-term effects on deep-sea ecosystems 2 , but the ability of seafloor ecosystems to recover from impacts over decadal scales is poorly understood 3 . Here we show that, four decades after a test mining experiment that removed nodules, the biological impacts in many groups of organisms are persistent, although populations of several organisms, including sediment macrofauna, mobile deposit feeders and even large-sized sessile fauna, have begun to re-establish despite persistent physical changes at the seafloor. We also reveal that areas affected by plumes from this small-scale test have limited detectable residual sedimentation impacts with some biological assemblages similar in abundance compared to control areas after 44 years. Although some aspects of the modern collector design may cause reduced physical impact compared to this test mining experiment, our results show that mining impacts in the abyssal ocean will be persistent over at least decadal timeframes and communities will remain altered in directly disturbed areas, despite some recolonization. The long-term effects seen in our study provide critical data for effective management of mining activities, if they occur, including minimizing direct impacts and setting aside an effective network of protected areas 4,5 .

Though internal waves cannot propagate vertically through weakly stratified fluid, if the depth of the weak stratification is sufficiently shallow, these waves can partially transmit through it. This paper quantitatively extends previous results on Cartesian internal wave tunneling to the case of axisymmetric wave fields and proposes a simple three-layer model. We show that there exists a smooth transition between the fully propagating and the tunneling regimes. We further reflect on the challenges set by the measurement of internal wave mode amplitudes in confined domains, and we discuss an innovative method to measure said amplitudes in this experimental and numerical context.

This study presents in situ, high-resolution optical measurements of particle size distributions (PSD) within sediment plumes generated by a pre-prototype deep seabed nodule collector vehicle operating in the abyssal Pacific Ocean. These measurements were obtained using a cutting-edge instrument, the LISST-RTSSV sensor. The data collected in situ reveal marked differences compared to previously reported laboratory-based, ex situ measurements. The grain size and other key particle shape characteristics are found to be dependent on multiple factors, including the collector vehicle maneuvers, the time elapsed following sediment discharge, and the complex hydrodynamic processes that generate the sediment in suspension. Significantly, the PSD from a highly complex succession of straight-line maneuvers converges to that of the canonical case of a simple straight-line driving maneuver within a timescale of ten minutes. Our results underscore the importance of parameterizing sediment plume transport models based on well-informed, comprehensive PSDs of detrained suspended sediment measured in situ at adequate timescales and in regions no longer strongly influenced by active and complex hydrodynamic processes.

Abstract The time series of near‐bottom temperatures collected from September 2018 until August 2020 from an array of three current‐ and pressure‐recording inverted echo sounders showed quasi‐seasonal and quasi‐monthly (∼28 days) variations at a depth of ∼1,300 m near the Chukchi slope in the western Arctic Ocean. They revealed an increase of ∼0.1°C during the winter‐spring period compared with the summer‐fall period. These variations were observed in the data‐assimilated Hybrid Coordinate Ocean Model (HYCOM) outputs near the observation site (correlation coefficient &gt;0.7). They confirmed that variations in near‐bottom temperature are related to changes in the intensity of the Atlantic Water (AW) boundary current, concurrent with the deepening of the lower AW layer by approximately 50 m. The difference in sea surface height (SSH) between the Canada Basin and the Chukchi Shelf increased because of the negative wind stress curl (WSC) and retarded the AW boundary current according to the geostrophic effect. When the near‐bottom temperature increased during the winter‐spring period, the SSH in the Chukchi Shelf was lower than that in the summer‐fall period because of the less negative WSC. Quasi‐monthly variations were related to SSH on the Chukchi Shelf owing to the negative WSC. HYCOM outputs from 1994 to 2015 showed that the AW boundary current weakened more recently than in the past due to the increased melting of sea ice. The results imply that a longer sea‐ice‐free season in the Arctic amplifies changes in the AW boundary current and deep ocean temperature owing to increased atmospheric forcing.

Descrip,on Mathema,cal Defini,on Units Essen,al Ocean Variable □□ ! , □□ " , □□ # , □□ $ Subsurface turbulent fluxes □□ ! = - □□ □□ % {□□ & □□ & } ≈ □□ ' □□ ( W kg -1 □□ " = -□□□□ ) {□□ & □□ & } ≈ □□□□ ) □□ * □□□□ □□□□ W m -2 □□ # = -{□□ & □□ & } ≈ □□ # □□□□ □□□□ psu m s-1 □□ $ = -{□□ & □□ & } ≈ □□ $ □□□□ □□□□ [C] m sK m -1 , psu m -1 , [C] m -1b is buoyancy; q is enthalpy; S is the salinity concentration; and C is an arbitrary scalar tracer concentration. u′,v′,w′ are microscale perturbations of ocean velocities. □□ is the water density. g is the gravitational constant. N is the buoyancy frequency. cp is the water thermal capacity. □□ is the potential temperature. k0,kc represents the wavenumber range for spectral integration. □□ $ ! and □□ & ! are the spectra of vertical shear and temperature gradient.Reminder: Figures, tables, and images will be published under a Creative Commons CC-BY licence and permission must be obtained for use of copyrighted material from other sources (including re-published/adapted/modified/partial figures and images from the internet). It is the responsibility of the authors to acquire the licenses, to follow any citation instructions requested by third-party rights holders, and cover any supplementary charges.

Near&amp;#8208;inertial waves are waves propagating in the interior of the ocean. Created by surface storms, they have the potential to influence the ocean environment by inducing vertical mixing. Compared to other oceans, the Arctic Ocean has low near-inertial wave activity, but might be changing. It is a challenge, however, to predict near-inertial wave activity in the Arctic Ocean due to its intricate vertical salinity and temperature stratification. Our in-situ campaign has obtained the first direct deep current measurements revealing notable temporal and spatial variability of deep near-inertial waves in the western Arctic Ocean. These observations are an important step towards a clearer depiction of the evolving energy budget, and concomitant mixing, associated with potentially high impact near-inertial wave activity in an increasingly ice-free Arctic Ocean.

We contend that ocean turbulent fluxes should be included in the list of Essential Ocean Variables (EOVs) created by the Global Ocean Observing System. This list aims to identify variables that are essential to observe to inform policy and maintain a healthy and resilient ocean. Diapycnal turbulent fluxes quantify the rates of exchange of tracers (such as temperature, salinity, density or nutrients, all of which are already EOVs) across a density layer. Measuring them is necessary to close the tracer concentration budgets of these quantities. Measuring turbulent fluxes of buoyancy ( J b ), heat ( J q ), salinity ( J S ) or any other tracer requires either synchronous microscale (a few centimeters) measurements of both the vector velocity and the scalar (e.g., temperature) to produce time series of the highly correlated perturbations of the two variables, or microscale measurements of turbulent dissipation rates of kinetic energy ( ϵ ) and of thermal/salinity/tracer variance ( χ ), from which fluxes can be derived. Unlike isopycnal turbulent fluxes, which are dominated by the mesoscale (tens of kilometers), microscale diapycnal fluxes cannot be derived as the product of existing EOVs, but rather require observations at the appropriate scales. The instrumentation, standardization of measurement practices, and data coordination of turbulence observations have advanced greatly in the past decade and are becoming increasingly robust. With more routine measurements, we can begin to unravel the relationships between physical mixing processes and ecosystem health. In addition to laying out the scientific relevance of the turbulent diapycnal fluxes, this review also compiles the current developments steering the community toward such routine measurements, strengthening the case for registering the turbulent diapycnal fluxes as an pilot Essential Ocean Variable.

Abstract Results and key insights are presented from in situ, high-resolution optical measurements of particle size distributions (PSD) for sediment plumes generated by a pre-prototype deep seabed nodule collector vehicle operating in the abyssal Pacific Ocean. The data show marked differences compared to previously reported laboratory-based, ex situ measurements. The in situ suspended sediment grain size and other key particle shape characteristics are found to be dependent on multiple factors such as the collector vehicle maneuvers, the time elapsed following discharge, and the complex hydrodynamic processes that generate the sediment in suspension. At the measuring instrument mounting height of 5m above the seabed, the PSD from a highly complex succession of straight-line maneuvers is found to converge to that of the canonical case of a simple straight-line driving maneuver within a timescale of ten minutes. Practically, our findings emphasize the need for parameterization of sediment plume transport models based on well-informed comprehensive PSDs of detrained suspended sediment measured in situ at adequate timescales and in regions no longer actively affected by active and complex hydrodynamic processes.

Abstract The oceanic bottom mixed layer (BML) is a well mixed, weakly stratified, turbulent boundary layer. Adjacent to the seabed, the BML is of intrinsic importance for studying ocean mixing, energy dissipation, particle cycling and sediment-water interactions. While deep-seabed mining of polymetallic nodules is anticipated to commence in the Clarion-Clipperton Zone (CCZ) of the northeastern tropical Pacific Ocean, knowledge gaps regarding the form of the BML and its potentially key influence on the dispersal of sediment plumes generated by deep-seabed mining activities are yet to be addressed. Here, we report recent field observations from the German mining licence area in the CCZ that characterise the structure and variability of the BML locally. Quasi-uniform profiles of potential temperature extending from the seafloor reveal the presence of a spatially and temporally variable BML with an average local thickness of approximately 250 m. Deep horizontal currents in the region have a mean speed of 3.5 cm s $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> and a maximum speed of 12 cm s $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> at 18.63 ms above bottom over an 11 month record. The near-bottom currents initially have a net southeastward flow, followed by westward and southward flows with the development of complex, anticyclonic flow patterns. Theoretical predictions and historical data show broad consistency with mean BML thickness but cannot explain the observed heterogeneity of local BML thickness. We postulate that deep pressure anomalies induced by passing surface mesoscale eddies and abyssal thermal fronts could affect BML thickness, in addition to local topographic effects. A simplified transport model is then used to study the influence of the BML on the interplay between turbulent diffusion and sediment settling in the transport of deep-seabed mining induced sediment plumes. Over a range of realistic parameter values, the effects of BML on plume evolution can vary significantly, highlighting that resolving the BML will be a crucial step for accurate numerical modelling of plume dispersal.

We present an investigation of the resonance conditions governing triad interactions of cylindrical internal waves, i.e. Kelvin modes, described by Bessel functions. Our analytical study, supported by experimental measurements, is performed both in confined and unconfined axisymmetric domains. We are interested in two conceptual questions: can we find resonance conditions for a triad of Kelvin modes? What is the impact of the boundary conditions on such resonances? In both the confined and unconfined cases, we show that sub-harmonics can be spontaneously generated from a primary wave field if they satisfy at least a resonance condition on their frequencies of the form $\omega _0 = \pm \omega _1 \pm \omega _2$ . We demonstrate that the resulting triad is also spatially resonant, but that the resonance in the radial direction may not be exact in confined geometries due to the prevalence of boundary conditions – a key difference compared with Cartesian plane waves.