Vertical structure of mesoscale eddies is key to the eddy-induced heat/material transport that further affects the climate and marine ecosystem. This study explores the vertical structure of mesoscale eddies in the Kuroshio-Oyashio Extension region (KOE) and its underlying dynamics. By applying the hierarchical ascending classification to the observational and reanalysis datasets, we classify mesoscale eddies with three distinct kinds of vertical structures. Each kind of eddies exhibits clear spatial aggregation along a distinct zonal band. Eddies have core depths of 100-300 m in the northern part of the KOE and core depths of 300-500 m and 0-100 m in the southern. The eddy splitting or merging does not introduce new kind of eddy vertical structure but causes large intra-kind variability. The different kinds of eddy vertical structures can be partially accounted for by the inference from the baroclinic instabilities at the eddy generation sites.

Given the role played by the historical and extensive coverage of sea ice concentration (SIC) observations in reconstructing the long-term variability of Antarctic sea ice, and the limited attention given to model-dependent parameters in current sea ice data assimilation studies, this study focuses on enhancing the performance of the Data Assimilation System for the Southern Ocean (DASSO) in assimilating SIC through optimizing the localization and observation error estimate, and two assimilation experiments were conducted from 1979 to 2018. By comparing the results with the sea ice extent of the Southern Ocean and the sea ice thickness in the Weddell Sea, it becomes evident that the experiment with optimizations outperforms that without optimizations due to achieving more reasonable error estimates. Investigating uncertainties of the SIV anomaly modeling reveals the nonnegligible role played by the sea ice-ocean interaction during the SIC assimilation, implying the necessity of assimilating more oceanic and sea-ice observations.

The Nansha Islands comprise the largest atoll archipelago in the South China Sea, accommodating 15% of global atolls. In contrast to reef flats found elsewhere in the Indo-Pacific region that typically have grown close to modern sea level, a considerable portion of atoll rims there are composed of 10-20-m-deep reef flats. To better understand modern processes, particularly whether these deep reefs are host to modern physical reworking or instead may be relict features abandoned by sea-level rise, we conducted a mooring hydrodynamic observation from January to September on a 12-m-deep southwest-facing reef flat. These measurements show a predominance of seasonally-varying waves and stable, moderate tide-driven currents, similar to short-term observations at three adjacent deep-reef-flats. While the reef flat was protected from the northeast monsoon from January to May, the southwest monsoon from June to September caused prolonged exposure to large waves (mean Hs of 1.3 m; orbital velocity 0.22 m/s) and consistent cross-flat currents (0.08 m/s on average), resulting in near-bed skin-friction shear velocities of 0.02 m/s on average. These wave conditions are capable of forming and mobilizing bed ripples while entraining coarse coral sand (d50 = 1 mm) for over half a year. Estimates of potential sediment flux suggest the capability for combined waves and advective currents to deflate the 12-m-deep reef rim by up to 28 mm in 8 months. As these potential losses are similar to reef accretion rates, our measurements imply that modern processes could play a significant role in the maintenance of deep reef flats.

Because of a spring predictability barrier, the seasonal forecast skill of Arctic summer sea ice is limited by the availability of melt-season sea ice thickness (SIT) observations. The first year-round SIT observations, retrieved from CryoSat-2 from 2011–2020, are assimilated into the GFDL ocean–sea ice model. The model’s SIT anomaly field is brought into significantly better agreement with the observations, particularly in the Central Arctic. Although the short observational period makes forecast assessment challenging, we find that the addition of May–August SIT assimilation improves September local sea ice concentration (SIC) and extent forecasts similarly to the early addition of SIC assimilation. Although most regional forecasts are improved by SIT assimilation, the Chukchi Sea forecasts are degraded. This degradation is likely due to the introduction of negative correlations between September SIC and earlier SIT introduced by SIT assimilation, contrary to the increased correlations found in other regions.

The Barents Sea is one of the main pathways for warm and saline Atlantic Water (AW) entering the Arctic Ocean. It is an important region for water mass transformation and dense-water production that contribute to the Atlantic meridional overturning circulation. Here, we present data from three cruises and nine glider missions conducted between 2019 and 2022 in the western Barents Sea, and compare with historical data collected from 1950 to 2009. We present circulation pathways, hydrography, heat content and volume fluxes of Atlantic- and Arctic-origin waters. Our observations show that 0.9±0.1 Sv (1 Sv = 106 m3 s-1) of Atlantic-origin water reaches the Polar Front (PF) region before splitting into several branches and eventually subducting beneath Polar Water (PW). The observed increased heat content in the AW inflow over the past decades can be traced under the Polar front. The amount of heat stored in the basin north of the PF is determined by the density difference between AW and PW, and reached a maximum in the 90s when PW was particularly fresh. The inflow of Atlantic Water (AW) into the Barents Sea during the period from 2019 to 2022 exhibits a decrease in salinity of up to 0.1 g kg-1 compared to previous decades. Consequently, this leads to a reduction in the production of dense water, an increased temperature gradient across the PF, and a reduced poleward transport of warm water.

A collapse of the Atlantic Meridional Overturning Circulation (AMOC) would have substantial impacts on global precipitation patterns, especially in the vulnerable tropical monsoon regions. We assess these impacts using four state-of-the-art climate models with bistable AMOC. Spatial and seasonal patterns of precipitation change are remarkably consistent across models. We focus on the South American Monsoon (SAM), the West African Monsoon (WAM), the Indian Summer Monsoon (ISM) and the East Asian Summer Monsoon (EASM). Models consistently suggest substantial disruptions for WAM, ISM and EASM with shorter wet and longer dry seasons (-29.07\%,-18.76\% and -3.78\% ensemble mean annual rainfall change, respectively). Models also agree on changes for the SAM, suggesting rainfall increases overall, in contrast to previous studies. These are more pronounced in the southern Amazon (+43.79\%), accompanied by decreasing dry-season length. Consistently across models, our results suggest major rearranging of all tropical monsoon systems in response to an AMOC collapse.

Though precise, most LiDARs are vulnerable to position and pointing errors as deviations from the expected principal axis lead to projection errors on target. While fidelity of location/pointing solutions can be high, determination of uncertainty remains relatively limited. As a result, NASA’s 2021 Surface Topography and Vegetation Incubation Study Report lists vertical (horizontal, geolocation) accuracy as an associated parameter for all (most) identified Science and Application Knowledge Gaps, and identifies maturation of Uncertainty Quantification (UQ) methodologies on the STV Roadmap for this decade. The presented generalized Polynomial Chaos Expansion (gPCE) based method has wide ranging applicability to improve positioning, geolocation uncertainty estimates for all STV disciplines, and is extended from the bare earth to the bathymetric lidar use case, adding complexity introduced by entry angle, wave structure, and sub-surface roughness. This research addresses knowledge gaps in bathy-LiDAR measurement uncertainty through a more complete description of total aggregated uncertainties, from system level to geolocation, by applying a gPCE-UQ approach. Currently, the standard approach is the calculation of the Total Propagated Uncertainty, which is often plagued by simplifying approximations (e.g. strictly Gaussian uncertainty sources) and ignored covariances. gPCE intrinsically accounts for covariance between variables to determine uncertainty in a measurement, without manually constructing a covariance matrix, through a surrogate model of system response. Additionally, gPCE allows arbitrarily high order uncertainty estimates (limited only by the one-time computational cost of computing gPCE coefficients), accurate representation of non-Gaussian sources of error (e.g. wave height energy distributions), and direct integration of measurement requirements into the design of LiDAR systems, by trivializing the computation of global sensitivity analysis.

Modelled geospatial Lagrangian trajectories are widely used in Earth Science, including in oceanography, atmospheric science and marine biology. The typically large size of these dataset makes them arduous to analyze, and their underlying pathways challenging to identify. Here, we show that a Machine Learning unsupervised k-means++ clustering method can successfully identify the pathways of the Labrador Current from a large set of modelled Lagrangian trajectories. The presented method requires simple pre-processing of the data, including a Cartesian correction on longitudes and a PCA reduction. The clustering is performed in a kernalized space and uses a larger number of clusters than the number of expected pathways. During post-processing, similar clusters are grouped into pathway categories by experts in the circulation of the region of interest. We find that the Labrador Current mainly follows a westward-flowing and an eastward retroflecting pathway (20% and 50% of the flow, respectively) that compensate each other through time in a see-saw behaviour. These pathways experience a strong variability of up to 96\%. We find that two thirds of the retroflection occurs at the tip of the Grand Banks, and one quarter at Flemish Cap. The westward pathway is mostly fed by the on-shelf branch of the Labrador Current, and the eastward pathway by the shelf-break branch. Pathways of secondary importance feed the Labrador Sea, the Gulf of St. Lawrence through the Belle Isle Strait, and the subtropics across the Gulf Stream.

Every austral spring when Antarctic sea ice melts, favorable growing conditions lead to an intense phytoplankton bloom, which supports much of the local marine ecosystem. Recent studies have found that Antarctic sea ice is predictable several years in advance, suggesting that the spring bloom might exhibit similar predictability. Using a suite of perfect model predictability experiments, we find that November net primary production (NPP) is potentially predictable seven to ten years in advance in many Southern Ocean regions. Sea ice extent predictability peaks in late winter, followed by absorbed shortwave radiation and NPP with a two to three months lag. This seasonal progression of predictability supports our hypothesis that sea ice and light limitation control the inherent predictability of the spring bloom. Our results suggest skillful interannual predictions of NPP may be achievable, with implications for managing fisheries and the marine ecosystem, and guiding conservation policy in the Southern Ocean.

This study investigates hydrodynamics and short-term temperature fluctuations at high-latitude coral reefs, focusing on Sodwana Bay in South Africa. A refined hydrodynamic model nested within a global ocean model was developed to investigate s temperature anomalies. On-reef hydrodynamics were also measured using Tilt Current Meters over eight months between 25/08/2021 and 16/05/2022 to describe the on-reef hydrodynamics at Sodwana during temperature anomaly events. During temperature anomaly events, the predominant current direction is south-southwestward, occasionally reversing to the north with cold water temperature anomalies. Current speeds range from 0.1 to 0.2m/s, peaking at 0.35m/s at the shallow low rugosity site. The nested model, developed using the Delft 3D Flexible Mesh hydrodynamic modelling suite, successfully replicates the observed temperature anomalies in 2004. The nested modelled better replicates the temperature anomaly amplitudes compared to the reanalysed NEMO global ocean model due to the high model resolution around Sodwana. A nested hydrodynamic model is necessary for accurate analysis of short-term temperature fluctuations. A representative anomaly in February 2004 was investigated using the nested model. The anomaly was associated with remote upwelling of cold water near the Delagoa Peninsula, followed by advection towards Sodwana. As it reaches the region, the entire Sodwana region is engulfed by the cold upwelled water. The model revealed that local upwelling occurs within the Sodwana canyons during this event, making the water in the canyons 1 °C colder than the surrounding water. When the locally upwelled water spreads over the reef system, the anomaly amplitude is enhanced by approximately 20%.

Winter Euro-Atlantic atmospheric blocking events have significant socioeconomical impacts as they cause various types of weather extremes in a range of regions. According to current climate projections, fewer of these blocking events will occur as temperatures rise. However, the timing of such a reduction is currently highly uncertain. Meanwhile, recent studies indicate that using climate models with high enough ocean resolutions to simulate mesoscale eddies improve simulated winter Euro-Atlantic blocking events significantly. In this paper, we show from a large ensemble of climate simulations based on the highest emission scenario that largely prominent and coarsely resolved non-eddying climate models project a noticeable significant decline in blocking frequencies from the 2030s-2040s, whereas blocking statistics in eddy-permitting simulations are noticeably decreasing only from years 2060s. Our result suggests with a strong level of confidence that winter blocking activity over the next several decades will keep being dominated by internal variability.

Scientific programming has become increasingly essential for manipulating, visualizing, and interpreting the large volumes of data acquired in earth science research. Yet few domain-specific instructional approaches have been documented and assessed for their effectiveness in equipping geoscience undergraduate students with coding and data literacy skills. Here we report on an evidence-based redesign of an introductory Python programming course, taught fully remotely in 2020 in the School of Oceanography at the University of Washington. Key components included a flipped structure, activities infused with active learning, an individualized final research project, and a focus on creating an accessible learning environment. Cloud-based notebooks were used to teach fundamental Python syntax as well as functions from packages widely used in climate-related disciplines. By analyzing quantitative and qualitative student metrics from online learning platforms, surveys, assignments, and a student focus group, we conclude that the instructional design facilitated student learning and supported self-guided scientific inquiry. Students with less or no prior exposure to coding achieved similar success to peers with more previous experience, an outcome likely mediated by high engagement with course resources. We believe that the constructivist approach to teaching introductory programming and data analysis that we present could be broadly applicable across the earth sciences and in other scientific domains.

A holistic review is given of the Southern Ocean dynamic system, in the context of the crucial role it plays in the global climate and the profound changes it is experiencing. The review focuses on connections between different components of the Southern Ocean dynamic system, drawing together contemporary perspectives from different research communities, with the objective of ‘closing loops’ in our understanding of the complex network of feedbacks in the overall system. For the purposes of this review, the Southern Ocean dynamic system is divided into four main components: large-scale circulation; cryosphere; turbulence; and gravity waves. Overviews are given of the key dynamical phenomena for each component, before describing the linkages between the components. The reviews are complemented by an overview of observed Southern Ocean trends and future climate projections. Priority research areas required to improve our understanding of the Southern Ocean system are identified.

A generalised methodology to deploy different types of vertical coordinate systems in arbitrarily defined time-invariant local areas of quasi-Eulerian numerical ocean models is presented. After detailing its characteristics, we show how the novel localisation method can be used to improve the representation of the Nordic Seas overflows in the UK Met Office NEMO-based eddy-permitting global ocean configuration. Three z*-levels with partial steps models localising different types of terrain-following vertical coordinates in the proximity of the Greenland-Scotland ridge are developed and compared against a control. Experiments include a series of idealised and realistic numerical simulations where the skill of the models in computing pressure forces, reducing spurious diapycnal mixing and reproducing observed properties of the Nordic Seas overflows are assessed. Numerical results prove that the localisation approach proposed here can be successfully used to embed terrain-following levels in a global geopotential levels-based configuration, provided that the localised vertical coordinate chosen is flexible enough to allow a smooth transition between the two. In addition, our experiments show that deploying localised terrain-following coordinates via the multi-envelope method allows the crucial reduction of spurious cross-isopycnal mixing when modelling bottom intensified buoyancy driven currents, significantly improving the realism of the Nordic Seas overflows simulations in comparison to the other models. Important hydrographic biases are found to similarly affect all the realistic experiments and a discussion on how their interaction with the type of localised vertical coordinate affects the accuracy of the simulated overflows is provided.

The Atlantic Meridional Overturning Circulation (AMOC) is considered to be a tipping element in the Earth System with multiple stable states. Here, we investigate the multiple equilibria window of the AMOC within a coupled ocean circulation-carbon cycle box model. We show that adding couplings between the ocean circulation and the carbon cycle model affects the multiple equilibria window of the AMOC. Increasing the total carbon content of the system will widen the multiple equilibria window of the AMOC, since higher atmospheric pCO2 values are accompanied by stronger freshwater forcing over the Atlantic ocean which acts to increase the window. Our results suggest that future changes in the marine carbon cycle can influence AMOC stability in future climates.

Ma. Eugenia Allende-Arandía1, Rodrigo Duran2,3, Laura Sanvicente-Añorve4, Christian M. Appendini1,*1Laboratorio de Ingeniería y Procesos Costeros, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Puerto de abrigo s/n, Sisal, Yucatán 97356, México2National Energy Technology Laboratory, United States Department of Energy, Albany OR, United States.3Theiss Research, La Jolla, CA, United States4Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad de México, C.P. 04510.Corresponding author: Christian M. Appendini (cappendinia@iingen.unam.mx )

A document by Kyle Duncan. Click on the document to view its contents.

The Salish Sea is a semi-enclosed sea between Vancouver Island and the coast of British Columbia and Washington State, invaluable from both an economic and ecologic perspective. Here we explore the contribution of Pacific water masses to the flow through Juan de Fuca Strait (JdF), the Salish Sea’s primary connection to the Pacific Ocean. Quantitative Lagrangian particle tracking within Ariane, an offline Lagrangian tool capable of volume transport calculations, was applied to two numerical ocean models to track the paths and physical properties of water parcels before entering JdF (CIOPS) and within the Salish Sea (SalishSeaCast). During summer upwelling, flow from the north shelf and offshore dominate Pacific inflow, while during winter downwelling, flow from the south shelf and surface flow from the Columbia River plume are the dominant Pacific sources. A weaker and less consistent estuarine flow regime in the winter leads to less Pacific inflow overall and a smaller percentage of said inflow reaching the Salish Sea’s inner basins than in the summer. Nevertheless, it was found that winter dynamics are a large driver of interannual variability, in part due to the anti-correlated behaviour and distinct properties of the two dominant winter sources. This analysis extends the knowledge on the dynamics of Pacific inflow to the Salish Sea and highlights the importance of winter inflow to interannual variability.

Eddies play a crucial role in shaping ocean dynamics by affecting material transport, and generating spatio-temporal heterogeneity. However, how eddies at different scales modulate biogeochemical transformation rates remains an open question. Applying a multi-scale decomposition to a numerical simulation, we investigate the respective impact of mesoscale and submesoscale eddies on nutrient transport and biogeochemical cycling in the California Current System. First, the non-linear nature of biological nutrient uptake results in a 50% reduction in primary production in the presence of eddies. Second, eddies shape the vertical transport of nutrients with a strong compensation between mesoscale and submesoscale. Third, the eddy effect on nutrient uptake is controlled by the covariance of temperature, nutrient and phytoplankton fluctuations caused by eddies. Our results shed new light on the tight interaction between non-linear fluid dynamics and ecosystem processes in realistic eddy regimes, highlighting the importance of both mesoscale and submesoscale variability.

Acoustic backscatter, velocimetry measurements of the nearbed velocity profiles, and thermistor chain measurements of the temperature stratification were used to understand the bottom boundary layer flows and associated sediment transport processes in 35 meters water depth on the California shelf off of Point Sal where the bottom sediment consist of fine sand with median grain size diameter of $d_{50}=0.1$ mm. The observations show that the nearbed flow is dominated by the bore of a shoaling internal tide whose steepening front generated a series of internal solitary waves (ISW) with a 15-min period superposed on the tail of the bore. The bore-induced nearbed flow was strongly asymmetric with 20 cm/s seaward directed flow under the bore trough that exceeded the bottom stress threshold for mobilization of the 0.1 mm sand, and 5-10 cm/s onshore flow during the tail of the bore that produced only subcritical bottom stress. The ISWs induced symmetric 5-10 cm/s nearbed velocity which however combined with the bore tail to produce onshore flows under the wave crests with bottom stress that also exceeded the sediment mobilization threshold.

Air-sea exchange of carbon dioxide (CO$_2$) in the Southern Ocean plays an important role in the global carbon budget. Previous studies have suggested that flow around topographic features of the Southern Ocean enhances the upward supply of carbon from the deep to the surface, influencing air-sea CO$_2$ exchange. Here, we investigate the role of seafloor topography on the transport of carbon and associated air-sea CO$_2$ flux in an idealized channel model. We find elevated CO$_2$ outgassing downstream of a seafloor ridge, driven by anomalous advection of dissolved inorganic carbon. Argo-like Lagrangian particles in our channel model sample heterogeneously in the vicinity of the seafloor ridge, which could impact float-based estimates of CO$_2$ flux.

A document by Clara Orbe. Click on the document to view its contents.

A document by Clara Orbe. Click on the document to view its contents.

These Earth Energy Budgets (EEBs) came to prominence in 1997 when Kiehl and Trenberth produced their EEB known commonly as KT97. They have regularly come under attack. Primarily they show the Earth emitting 300% more radiation than it receives from the Sun. This energy is being generated out of nothing and violates the 1 st Law of Thermodynamics. They also show the Sun shining on the dark side of the Earth, something that just doesn't happen. All the radiation data in these EEBs, with the exception of Long Wave Down LWD and Long Wave Up LWU infrared IR radiation at the surface, have been divided by 4. This shows the Sun shining equally on all 4 quadrants of the Earth. This has the effect of having the Earth emitting 300% more radiation than it receives from the Sun. This 300% extra radiation is supposedly being generated out of nothing by a greenhouse effect GHE in the atmosphere. It seems apparent that this divide by 4 system is being used as a means of justifying the GHE theory. IR radiation is 100 times less energetic than visible radiation. That means the 322 W/m 2 of IR LWD is the equivalent of 3.22 W/m 2 of visible or Short Wave Down SWD radiation from the Sun. Since it appears these EEBs are being used to calibrate climate models, it has become necessary to review these EEBs and that in turn led to it becoming necessary to generate a new Earth Energy Budget to bring some realism back into them. This paper produces a new Earth Energy budget based on measured data. The Earth receives 1,361 W/m 2 of Short Wave Down SWD solar radiation at the top of atmosphere TOA and 1,361 W/m 2 of Short Wave Up SWU and LWU arrive back at the TOA. 589 W/m 2 of solar radiation is absorbed in the surface and 589 W/m 2 of LWU, latent heat and thermals is emitted by the surface. There is no mystery radiation being generated in the atmosphere and the budget is in balance.