The Southern Ocean (SO) south of 35°S represents a small source of natural inorganic carbon for the atmosphere but a major sink of anthropogenic carbon. The magnitude of the total (natural plus anthropogenic) carbon sink strongly depends on the rate at which carbon is subducted below the mixed layer. We use a global ocean model at eddying resolution under preindustrial and historical conditions to provide a detailed view of total and anthropogenic dissolved inorganic carbon (DIC) pathways across and within the time-varying mixed layer of five physically consistent regions. Within each region, subduction fluxes at the mixed layer base are decomposed into advective and diffusive contributions to determine which process dominates. Total DIC is found to be obducted south of the Antarctic Circumpolar Current (ACC), transferred northward within the mixed layer and subducted north of the ACC. This results in a net obduction of 11.2 PgC/year, with advective processes dominating the total transfer (67%). Anthropogenic carbon is taken up in all regions but anthropogenic DIC is mainly subducted north of the ACC, the carbon taken up in the south being advected northward within the mixed layer before being subducted. This subduction (1.05 PgC/year) is achieved mainly through advection and diffusion, which dominate respectively north and south of the Subantarctic Front. Advective subduction fluxes show strong zonal variations and are increased near major topographic features and boundary currents. Our results suggest that we need to untangle advective and diffusive pathways regionally in order to understand how carbon subduction will evolve.

We measure energy spectra of electrons and gamma rays of electromagnetic avalanches developed in the electrified atmosphere as they arrive at the earth’s surface at 3200 m height where Aragats research station is located. We compare intensities and spectra shapes of 2 thunderstorm ground enhancements (TGE) observed in June and September 2020 with simulated ones. Although, the variants of electric field strength and topology assumed in the simulations are too simplified to reproduce the rather complicated and dynamic nature of the atmospheric electric field the closeness of several measured and observed parameters allows us to confirm that the relativistic runaway electron avalanches (RREA) is the origin of TGE, and to outline most probable characteristics of the atmospheric electric field for particular observed TGE events.

Increasing droughts and related water losses challenge lake systems. We analyzed water and sediment samples from five lakes in five subsequent dry and rainy seasons to study lakes’ vulnerability at times of significant environmental change, and to revisit the “old question” of whether different tropical lake water types can be observed in more complex datasets to better understand their limnological status, differences between lake types, and to broaden their baseline database for subsequent research. High temperatures combined with reduced oxygen levels (<<80% saturation) impose challenging boundary conditions for all biotas. Clearwater, black-, and whitewater can be differentiated by their signatures in dissolved ions, dissolved organic carbon, and selected major, minor and trace elements in water and sediment. Lake waters resembled remote rainwater. Lake sediment composition was compared with that of ‘terra firme’ soils in surrounding catchments for 47 chemical elements including carbon and nitrogen, macro- and micronutrients. With few exceptions (Ti; REE), sediment element concentrations showed mostly depletion when compared to the upper continental crust, reflecting regional soil chemistry and ongoing depletion of surrounding soils due to deforestation and changing landcover. Sediments act as intermediate sinks for eroded soil materials and show increasing buffer capacity from clearwater < blackwater < whitewater lakes. Under conditions of climate change, especially in areas close to the equator, the already pronounced oxygen depletion will pose further challenges for aquatic life. Lake, pisciculture, and catchment management should be adapted accordingly.

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Leigh Stadlera, Songo Anele Benyaa, Gina Ziervogela, Petra Holdena

Seismic velocity inversion of upper crustal structures in deep sea is challenging, as the unique condition of thick water column often limits the applicability of conventional inversion techniques. For example, while dispersion curves of guided P waves are commonly utilized for estimating subsurface P-wave velocity in land and shallow water environments, these waves have remained in obscurity in deep-water environments due to interference from subseafloor reflections, making them difficult to observe and, until now, unobserved. In this work, we report the first observation of guided P waves in deep water from multichannel seismic data and successfully extract multimode dispersion curves. The dispersive modes of deep water guided P waves are controlled by layered medium beneath the seafloor. Analyzing the dispersive modes of deep water guided P waves provides a tool for subsurface structural inversion in deep water environments.

Relativistic electron precipitation (REP) refers to the release of high energy electrons initially trapped in the outer radiation belt that precipitate into the Earth’s upper atmosphere. REP plays an important role in the magnetosphere as it contributes to the fast depletion of radiation belt electron flux. This study presents a statistical analysis of the REP observations made by the Calorimetric Electron Telescope (CALET) experiment on board the International Space Station (2015- present). Specifically, a catalog based on count rates from the two top scintillators constituting the top charge detector, sensitive to electrons with energies $>$1.5 MeV and $>$3.4 MeV, respectively. Data from the CALET experiment reveals a previously unreported semi-annual variation in the occurrence of REP events. The REP periodicities are similar to those observed for trapped electrons in the outer belt, and correlates with the occurrence of solar wind high-speed streams and the solar cycle variations.

A document by Drew Cochran. Click on the document to view its contents.

A document by Hirohiko Masunaga. Click on the document to view its contents.

A document by Kaan Cökerim. Click on the document to view its contents.

Amidst the nationwide flooding triggered by the rainy season compounded by El Niño, this study endeavors to devise a sophisticated mathematical model geared towards enhancing the efficiency of open circular channels. Focusing on key parameters like depth, velocity, and pressure within the context of incompressible, Newtonian, and steady flow dynamics, we aim to meticulously analyze their interplay. By delving into the impact of depth on flow characteristics, the influence of pressure on velocity, and the modulation of Reynolds and Froude numbers on velocity, our investigation unveils crucial insights. Leveraging MATLAB, we meticulously derive numerical solutions and visually represent our findings through insightful graphs. Given the inherent non-linearity of the governing equations; the continuity and momentum equations of motion. We used the finite difference method for the resolution. This robust model holds promise for diverse applications spanning water supply, treatment facilities, and irrigation networks, offering a comprehensive tool for optimizing operational efficiency.

The objective of this study is to evaluate the potential for History Matching (HM) to tune a climate system with multi-scale dynamics. By considering a toy climate model, namely, the two-scale Lorenz96 model and producing experiments in perfect-model setting, we explore in detail how several built-in choices need to be carefully tested. We also demonstrate the importance of introducing physical expertise in the range of parameters, a priori to running HM. Finally we revisit a classical procedure in climate model tuning, that consists of tuning the slow and fast components separately. By doing so in the Lorenz96 model, we illustrate the non-uniqueness of plausible parameters and highlight the specificity of metrics emerging from the coupling. This paper contributes also to bridging the communities of uncertainty quantification, machine learning and climate modeling, by making connections between the terms used by each community for the same concept and presenting promising collaboration avenues that would benefit climate modeling research.

Based on observations from the Magnetospheric Multiscale mission, this study presents an analysis of a short large-amplitude magnetic structures (SLAMS) event with simultaneous occurrence of low- and high-frequency magnetosonic whistler waves. It was found that low-frequency magnetosonic whistler waves around the lower-hybrid frequency emerge in the presence of solar wind ions and local low-energy ions in the trailing region of SLAMS. Additionally, counter-propagating whistler waves (the high-frequency branch of the magnetosonic whistler wave) are observed within SLAMS, coinciding with a perpendicular temperature anisotropy in the electron population. Instability analyses demonstrate that these low-frequency waves are induced by the two-stream instability associated with the cross-field drift of low-energy ions relative to electrons, while whistler waves are locally generated by the whistler anisotropy instability. Our results shed light on the impact of SLAMS on particle and wave dynamics in the terrestrial foreshock.

The objective is to demonstrate that spatially variable ice-surface roughness is an important, and so-far overlooked, component of melt processes in the Greenland Ice Sheet (GrIS), linking the analysis of spatial ice-surface roughness (SISR) derived from satellite laser altimeter data with a new regional energy balance model. Specific results are: (1) SISR can be calculated from ICESat Geoscience Laser Altimeter System (GLAS) data for the GrIS. (2) Seasonal and interannual changes of SISR are reflected in satellite-altimetry-based roughness maps, demonstrated for GLAS data. (3) Current regional climate models largely utilize roughness as a constant value in space and time. Here, we develop a new Regional Energy Balance Model (REBM) that is sensitive to SISR, using the same physical principles as the Integrated Forecasting System (IFS), constrained by climate fields of the Regional Atmospheric Climate Model (RACMO2). (4) A control study is carried out to ensure that REBM works correctly. (5) Melt energy of the GrIS calculated by REBM using SISR results in much higher melt values than predicted by regional climate models (RACMO2, IFS), which underestimate melting. (6) Application of the approach using REBM to the GrIS, driven by seasonally and interannually variable SISR, highlights regional and temporal differences in sensible heat flux and thus melt differences. In summary, SISR explains some of the discrepancy between observed and modeled melting in the GrIS. This study serves as a proof of concept for an approach that establishes mathematical and physical concepts for linking satellite altimeter measurements, SISR and energy balance modeling.

The North Icelandic Jet (NIJ) is a significant contributor to the lower limb of the Atlantic Meridional Overturning Circulation, supplying one-third to one-half of the overflow water transport through Denmark Strait, including the densest portion. Dense water produced in the Nordic Seas is banked up along the slope north of Iceland and can flow relatively unimpeded across the Denmark Strait sill as part of the NIJ. Major uncertainties remain regarding the mechanisms contributing to the emergence of the NIJ northeast of Iceland. This study investigates these mechanisms using a novel setup with a high-resolution, idealized model for the north Icelandic slope. Initially, we set up a channel model along the slope north of Iceland with differing slope geometry, no external forcing, and horizontally uniform initial and boundary conditions based on observations. Subsequently, we iteratively impose highly idealized inflows and outflows as boundary conditions in the west, emulating the North Icelandic Irminger Current (NIIC) inflow and dense NIJ outflow through Denmark Strait. The model consistently replicates key features of the NIJ, such as its mid-depth intensified core associated with diverging isopycnals away from the slope. Our results corroborate that a steeper slope, a stronger NIIC-like current, and stronger cross-slope density gradients promote instabilities closely related to the emerging NIJ-like current. Furthermore, the variability of the models’ NIJ-like current is largely associated with passing eddies, which might explain some of the observed occupations where the NIJ features a double-core structure.

As well as strong upward propagation of planetary waves from the troposphere, the state of the stratospheric mean flow has been recognized as a key factor for the occurrence of stratospheric sudden warmings (SSWs). The modification of the mean flow to a suitable state for an SSW occurrence is called “vortex preconditioning”. Recently, increasing attention has been paid to the role of gravity waves (GWs) in the preconditioning mechanism. However, because of the limited availability of datasets covering the whole neutral atmosphere, much uncertainty still exists in the role of GWs in the preconditioning. The aim of this study is to investigate the mechanism of modification of the mean flow in the stratosphere and mesosphere before SSWs from a climatological viewpoint and elucidate the role of GWs in it. We use two state-of-the-art datasets covering the whole neutral atmosphere: a 17-year medium-resolution reanalysis dataset and the output data from hindcast simulations performed with a GW-permitting general circulation model. It is shown that the second principal component of the zonal-mean zonal wind in the stratosphere and mesosphere tends to show a maximum prior to an SSW, characterizing preconditioning. GW forcing alters the structure of the upper part of the jet and contributes to the preconditioning along with planetary waves. Comparison of GW forcing between the reanalysis and GW-permitting model suggests that the magnitude of parameterized GW forcing is approximately half that of the GW forcing in the polar upper stratosphere where the forcing is responsible for the preconditioning.

We train random and boosted forests, two machine learning architectures based on regression trees, to emulate a physics-based parameterization of atmospheric gravity wave momentum transport. We compare the forests to a neural network benchmark, evaluating both offline errors and online performance when coupled to an atmospheric model under the present day climate and in 800 and 1200 ppm CO2 global warming scenarios. Offline, the boosted forest exhibits similar skill to the neural network, while the random forest scores significantly lower. Both forest models couple stably to the atmospheric model, and control climate integrations with the boosted forest exhibit lower biases than those with the neural network. Integrations with all three data-driven emulators successfully capture the Quasi-Biennial Oscillation (QBO) and sudden stratospheric warmings, key modes of stratospheric variability, with the boosted forest more accurate than the random forest in replicating their statistics across our range of carbon dioxide perturbations. The boosted forest and neural network capture the sign of the QBO period response to increased CO2, though both struggle with the magnitude of this response under the more extreme 1200 ppm scenario. To investigate the connection between performance in the control climate and the ability to generalize, we use techniques from interpretable machine learning to understand how the data-driven methods use physical information. We leverage this understanding to develop a retraining procedure that improves the coupled performance of the boosted forest in the control climate and under the 800 ppm CO2 scenario.

Positions of earthquakes over 5 th magnitude were investigate in Taiwan region and adjacent Philippine Sea Plate. Purpose of this paper was to establish earthquakes tidal periods in range of Moon sidereal rotation cycle. Because sidereal Moon cycle reflects variation in length of day of Earth, positions of earthquakes on this graph stated positions on Moon's orbit and from it followed the tidal frequences knowing time. 849 earthquakes after declusterization were investigated in three time periods 1962-1982, 1983-2002 and 2003-2024. Histograms of earthquakes compiled for Moon crossing equator from south, reaching maximum Moon declination, reaching Moon equator from north and reaching maximum negative declination, presented tidal frequence 6.83 days, 13.66 days and their multiples. By this way stated earthquake occurrence periods are only 31.8 %, but remaining earthquakes have also tidal origin given tectonic position on Taiwan and cumulative action of northsouth and westward directing forces.