We document magnetic mineral diagenesis with high resolution magnetic susceptibility, hysteresis, isothermal remanent magnetization, and other rock magnetic measurements through a shallow sulfate-methane transition (SMT) at Perseverance Drift-a high-accumulation rate Holocene biosiliceous Antarctic marine sediment deposit. The structure of the SMT is defined with porewater measurements from the same core, allowing direct comparison. Dissolution of the detrital (titano)magnetite assemblage, with preferential dissolution of stochiometric magnetite, occurs in the upper SMT. Higher coercivity magnetic minerals dissolve more slowly, continuing to dissolve through the entire SMT and could be a source of ferric iron for microbial respiration following exhaustion of porewater sulfate, as suggested by accumulation of porewater ferrous iron below the SMT. Superparamagnetic ferrimagnetic mineral enrichment/depletion occurs in three phases through the SMT and is coupled tightly to the availability of dissolved ferrous iron relative to dissolved sulfide. High concentrations of authigenic remanence-bearing iron sulfides, including greigite and hexagonal 3C pyrrhotite, which can be detected using remanence parameters but not in-field concentration dependent parameters, accumulate in a transient horizon at the base of the SMT during this early diagenesis, where sulfide is present but limited relative to dissolved ferrous iron. Formation of this remanence-bearing iron sulfide horizon is likely facilitated by continued iron reduction through the SMT. Non-steady state perturbations that shift the porewater profile, such as changes in carbon flux or sedimentation rate, can lead to preservation of these transient horizons, much like well documented preservation of manganese oxide layers in marine sediments following similar shifts to porewater profiles.

Coastal vegetated habitats like seagrass meadows can mitigate anthropogenic carbon emissions by sequestering CO2 as “blue carbon” (BC). Already, some coastal ecosystems are actively managed to enhance BC storage, with associated BC stocks included in national greenhouse gas inventories or traded on international markets. However, the extent to which BC burial fluxes are enhanced or counteracted by other carbon fluxes, especially air-water CO2 flux (FCO2) remains poorly understood. To this end, we synthesized all available direct FCO2 measurements over seagrass meadows made using a common method (atmospheric Eddy Covariance), across a globally-representative range of ecotypes. Of the four sites with seasonal data coverage, two were net CO2 sources, with average FCO2 equivalent to 44 - 115% of the global average BC burial rate. At the remaining sites, net CO2 uptake was 101 - 888% of average BC burial. A wavelet coherence analysis demonstrates that FCO2 was most strongly related to physical factors like temperature, wind, and tides. In particular, tidal forcing appears to shape global-scale patterns in FCO2, likely due to a complex suite of drivers including: lateral carbon exchange, bottom-driven turbulence, and pore-water pumping. Lastly, sea-surface drag coefficients were always greater than prediction for the open ocean, supporting a universal enhancement of gas-transfer in shallow coastal waters. Our study points to the need for a more comprehensive approach to BC assessments, considering not only organic carbon storage, but also air-water CO2 exchange, and its complex biogeochemical and physical drivers.

Motivated by the remarkably large propagation distances observed in turbidity currents near the mouth of the Congo River in Africa, a new model is proposed for their dynamics. It assumes that the erosion of solid particles from the bed underneath the current increases the density of the current such that the vortex rotational rate increases over the case of no erosion. If the rate of increase of vortex rotation is sufficient, the entrainment rate of fluid above the current is inhibited. As a consequence, the turbidity current propagates much farther than would be expected without the dynamic effect of acceleration.

The effects of temporal changes in the marine geoid on estimates of the ocean dynamic topography is being investigated. Influences from changes of land hydrology, ice sheets, Post-Glacial Rebound (PGR), and ocean and atmospheric dynamics are considered and the associated crustal deformation is included. The strongest signals are associated with the seasonal cycle caused by changes in terrestrial water content and ice sheets as well as the redistribution of atmospheric mass. Second to this is the importance of an overall trend caused by PGR and decreasing ice sheets over Greenland and Antarctica. On long spatial scales, the amplitude of regional trends estimated for the geoid height have a sizable fraction of those from Sea Level Anomaly (SLA) for the period 1993–2016, also after subtraction of steric height of the upper 1000m to analyze trends in deep ocean geostrophic currents. The estimated strong negative geoid height trend south of Greenland for the period 1993–2016 opposes changes in dynamic sea level for the same period thereby affecting past studies on changes of both the strength of the Subpolar Gyre based on SLA and the meridional overturning circulation on a section between Cape Farewell and Portugal applying ocean dynamic topography and hydrography. We conclude that temporal geoid height trends should be considered in studies of (multi-)decadal trends in sea level and circulation on large spatial scales based on altimetry data referenced to a geoid field.

Using long-term satellite altimeter data, a new streamline-based algorithm is developed to identify the Kuroshio intrusion types and describe the seasonal variations of related dynamical properties. Results from this new classification show that a mixing of leaping, looping and leaking streamlines is the dominant form of Kuroshio intrusion into the South China Sea (SCS). The leaping path is very stable and crosses the Luzon Strait mainly through the Balintang Channel regardless of seasons, while the streamlines leaking into the SCS is more likely to intrude via the channel between the Babuyan Island and the Camiguin Island. Large seasonal variations are found with the percentage of each kind of streamline and the Luzon Strait Transport (LST), but not with the intensity, width and current axis position of the Kuroshio. The along-streamline analysis reveals that the seasonal intrusion of the Kuroshio is essentially the seasonal variation of the cyclonic shear part of the flow. A possible physical mechanism is proposed to accommodate these seasonal characteristics based on globally the vorticity (torque work) balance between the basin-wide wind stress and the lateral friction, as well as locally the loss of balance between the torques of interior stresses and normal stresses both provided by the wall boundary, together with a plausible conjecture that the seasonally-reversing monsoon can significantly modify the torque of the interior stresses within the cyclonic shear part of the flow and thus responsible for the seasonal variation of the Kuroshio intrusion.

To clarify the impact of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a, and stable oxygen isotopic ratios (δ18O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Off the TIS, modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf and flowed along bathymetric troughs into the TIS cavity, where it met the ice shelf base and formed a buoyant mixture with glacial meltwater. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, DIC, TA, and nutrient concentrations on the surface of the ice front were decreased by photosynthesis and the dilution effect of meltwater from sea ice and the base of the ice shelf. The partial pressure of CO2 (pCO2) in surface water was reduced by photosynthesis and dilution, and the surface water became a strong CO2 sink for the atmosphere. The DIC and TA (normalized to salinity of 34.3 to correct for dilution effects) changed in a molar ratio of 106:16 because of phytoplankton photosynthesis. The decrease of pCO2 by more than 100 μatm with respect to mCDW was thus the result of photosynthesis. The nutrient consumption ratio suggested that enough iron was present in the water column to supply the surface layer via buoyancy-driven upwelling and basal melting of the TIS.

The Delaware River is a major freshwater supplier of New York City (NYC). Nearly half of NYC drinking water is supplied by inter-basin transfer of surface water stored in reservoirs within the upper reaches of the Delaware River. In its lower reaches, the Delaware River is a tidal estuary, and upstream freshwater discharge provides a critical control on estuary salinity. During the record 1950–1960’s drought, NYC water withdrawals exacerbated low flows. Estuary salinity reached levels that threatened freshwater intakes and groundwater recharge, resulting in legal action and Supreme Court decrees. We revisit this classic case study in coupled human and natural systems using the Energy Exascale Earth System Model (E3SM). The E3SM water management sub-model is updated to include inter-basin water transfer and reservoir-specific operating rules. Model simulations are developed to investigate competition between NYC water demand and in-stream flow targets needed to maintain estuary salinity within regulatory guidelines under historic and future climate. To our knowledge, this is a first demonstration of an Earth System Model simulation with inter-basin water transfer, which, in this study area, provides water for nearly five million people living outside the Delaware River basin in New York City and New Jersey.

The Canadian Arctic Archipelago (CAA) is vulnerable to climate warming, and with over 300 tidewater glaciers, is a hotspot for enhanced glacial retreat and meltwater runoff to the ocean. In contrast to Greenlandic and Antarctic systems, CAA glaciers and their impact on the marine environment remain largely unexplored. Here we investigate how CAA glaciers impact nutrient delivery to surface waters. We compare water column properties in the nearshore coastal zone along a continuum of locations, spanning those with glaciers (glacierized) to those without (non-glacierized), in Jones Sound, eastern CAA. We find that surface waters of glacierized regions contain significantly more macronutrients (nitrogen, silica, phosphorus) and micronutrients (iron, manganese) than their non-glacierized counterparts. Water column structure and chemical composition suggest that macronutrient enrichments are a result of upwelling induced by rising submarine discharge plumes, while micronutrient enrichments are driven directly by glacial discharge. Generally, the strength of upwelling and associated macronutrient delivery scales with tidewater discharge volume. Glacier-driven delivery of the limiting macronutrient, nitrate, is of particular importance for local productivity, while metal delivery may have consequences for regional micronutrient cycling given Jones Sound’s important role in modifying water masses flowing into the North Atlantic. Finally, we use the natural variability in glacier characteristics observed in Jones Sound to consider how nutrient delivery may be affected as glaciers retreat. The impacts of melting glaciers on marine ecosystems through both these mechanisms will likely be amplified with increased meltwater fluxes in the short-term, but eventually muted as CAA ice masses diminish.

We develop a hierarchy of simplified ocean models for coupled ocean, atmosphere, and sea ice climate simulations using the Community Earth System Model version 1 (CESM1). The hierarchy has four members: a slab ocean model, a mixed-layer model with entrainment and detrainment, an Ekman mixed-layer model, and an ocean general circulation model (OGCM). Flux corrections of heat and salt are applied to the simplified models ensuring that all hierarchy members have the same climatology. We diagnose the needed flux corrections from auxiliary simulations in which we restore the temperature and salinity to the daily climatology obtained from a target CESM1 simulation. The resulting 3-dimensional corrections contain the interannual variability fluxes that maintain the correct vertical gradients of temperature and salinity in the tropics. We find that the inclusion of mixed-layer entrainment and Ekman flow produces sea surface temperature and surface air temperature fields whose means and variances are progressively more similar to those produced by the target CESM1 simulation. We illustrate the application of the hierarchy to the problem of understanding the response of the climate system to the loss of Arctic sea ice. We find that the shifts in the positions of the mid-latitude westerly jet and of the Inter-tropical Convergence Zone (ITCZ) in response to sea-ice loss depend critically on upper ocean processes. Specifically, heat uptake associated with the mixed-layer entrainment influences the shift in the westerly jet and ITCZ. Moreover, the shift of ITCZ is sensitive to the form of Ekman flow parameterization.

Ice-shelf break-up is thought to be driven by a combination of various environmental factors that can be classified as oceanographic, glaciological and atmospheric. These contribute to different phases of the ice damaging process. However, physical processes driving ice-shelf collapse and rift propagation are still poorly understood. A few studies have suggested that ice-shelf rifting can be highly influenced by the rift’s infill. In particular, ice melange, a heterogeneous mixture of sea ice, marine ice, and trapped icebergs, is thought to stabilize rift evolution, potentially slowing or halting rift growth. In this study, we investigate ocean dynamics associated with rifts in ice-shelves using the Massachusetts Institute of Technology ocean general circulation model. Our goal is to estimate the effects of rifts on ice-shelf melting and freezing processes and in turn on sub-ice shelf circulation. Enhanced (reduced) melting/freezing rates induced by ice-shelf rifts affect the physical properties of the volume confined between rift’s flanks. Here, we examine key hydrographic conditions on sensitivities to the cracked ice-shelf basal environment in an idealized set-up. We find that basal fractures modify the thermohaline circulation by accumulation of cold and fresh water in the rift’s open volume, which potentially is a prerequisite for ice melange formation. An improved representation of ice-ocean interactions below a fractured ice-shelf is a step toward a better understanding of rifting processes and, on a larger scale, of ice-shelves collapse. To further study this, we use a more realistic regional set-up of Larsen C in the Antarctic Peninsula.

The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project has deployed 194 profiling floats equipped with biogeochemical (BGC) sensors, making it one of the largest contributors to global BGC-Argo. Post-deployment quality control of float-based oxygen, nitrate, and pH data is a crucial step in the processing and dissemination of such data, as in-situ chemical sensors remain in early stages of development. In-situ calibration of chemical sensors on profiling floats using atmospheric reanalysis and empirical algorithms have been shown to bring accuracy to within 3 μmol O2 kg-1, 0.007 pH units, and 0.5 μmol NO3- kg-1. Routine quality control efforts utilizing these methods can be conducted manually through visual inspection of data to assess sensor drifts and offsets, but more automated processes are preferred to support the growing number of BGC floats and reduce subjectivity among delayed-mode operators. Here we present a methodology and accompanying software designed to easily visualize float data against select reference datasets and assess quality control adjustments within a quantitative framework. The software is intended for global use and has been used successfully in the post-deployment calibration and quality control of over 250 BGC floats, including all within the SOCCOM array. Results from validation of the proposed methodology are also presented which can provide a metric for tracking data adjustment quality through time.

Global ocean mean salinity (GMS) is a key indicator of the Earth’s hydrological cycle and the exchanges of freshwater between land and ocean, but its determination remains a challenge. Aside from traditional methods based on gridded salinity fields derived from in situ measurements, we explore estimates of GMS based on liquid freshwater changes derived from space gravimetry data corrected for sea ice effects. For the 2005-2019 period analyzed, the different GMS series show little consistency in seasonal, interannual, and long-term variability. In situ estimates show sensitivity to choice of product and unrealistic variations. A suspiciously large rise in GMS since ~ 2015 is enough to measurably affect halosteric sea level estimates and can explain recent discrepancies in the global mean sea level budget. Gravimetry-based GMS estimates are more realistic, inherently consistent with estimated freshwater contributions to global mean sea level, and provide a way to calibrate the in situ estimates.

Fronts, at both mesoscale and submesoscales, are generally hypothesized to play a significant role in mediating the transfer of tracers from the surface boundary layer into the interior. With the advent of computational capabilities numerous high resolution modeling studies have shown the enhancement of of vertical velocities with increasing horizontal resolution. In a carefully designed setup of an idealized channel partially blocked by meridional topography and forced by steady forcing, idealization of the Antarctic Circumpolar Current, we vary the horizontal resolution as the control parameter, and analyze the impact of enhanced vertical velocities on tracer subduction. It is found that the submesoscale-permitting simulations flux far more tracer downward than the lower resolution simulations, the 1km simulation takes up 50\% more tracer compared to the 20km simulation, despite the increased restratifying influence of the resolved submesoscale processes. A spectral decomposition of the flow and fluxes illuminated the relative importance of scales, and the inefficiency of inertia-gravity waves in influencing tracer transport. To further understand the physical dynamics in these simulations we diagnosed how energy was being transferred between the mean and eddy kinetic and potential energy reservoirs (Lorenz energy cycles), and if changing the resolution influenced this exchange. In particular we focussed on separating the dynamics of the energy cycles that are active in the interior of the water column and those that are trapped near the surface. We also analyzed the inter-lengthscale exchange of energy to understand the detailed spectral dynamics of the turbulence that is resolved. Lastly, and probably most relevant to SWOT, we looked at the energy budgets in terms of velocity and pressure structure functions, to assess the potential for the future SWOT mission to directly measure the inter-scale energy transfers at the ocean surface.

The realization that changes within the Arctic have profound impacts on ecosystems and human populations across the globe has motivated greater attention. Yet major gaps remain in our understanding of the feedbacks, response, and resilience of coastal Arctic ecosystems, communities, and natural resources to current and future pressures. Most importantly, the Arctic coastal zone, a vulnerable and complex contiguous landscape of lakes, streams, wetlands, permafrost, rivers, lagoons, estuaries, and coastal seas—all modified by snow and ice—remains poorly understood. To improve our mechanistic understanding and prediction capabilities of land-ice-ocean interactions in the rapidly changing Arctic coastal zone, our team proposed a Field Campaign Scoping Study called Arctic-COLORS (Arctic-COastal Land Ocean inteRactionS) to NASA’s Ocean Biology and Biogeochemistry Program. Arctic-COLORS aims to quantify the response of the Arctic coastal environment to global change and anthropogenic disturbances – an imperative for developing mitigation and adaptation strategies for the region. Arctic-COLORS is unprecedented, as it represents the first attempt to study the nearshore coastal Arctic (from riverine deltas and estuaries out to the coastal sea) as an integrated land-ocean atmosphere-biosphere system. The overarching objective of Arctic-COLORS is to quantify the coupled biogeochemical/ecological response of the Arctic nearshore system to rapidly changing terrestrial fluxes and ice conditions, in the context of environmental (short-term) and climate (long-term) change. The science of our field campaign will focus on three key science themes and several overarching science questions per theme: (1) Effect of land on nearshore Arctic biogeochemistry (2) Effect of ice on nearshore Arctic biogeochemistry (3) Effects of future change (warming land and melting ice) on nearshore Arctic biogeochemistry This field campaign will be composed of an integrative measurement approach utilizing a broad range of proven sampling approaches from a multitude of platforms including autonomous vehicles to achieve sufficient seasonal and spatial coverage to resolve the science questions proposed by the Arctic-COLORS team as well as remote sensing and development of coupled physical-biogeochemical models.

The paper presents results of bathymetric surveys in the remote foreshore of the south Baltic (c.a. 1-2 Nm off the shoreline at depths of around 16-20 m). Measurements were collected twice in the vicinity of the Coastal Research Station (CRS) in Lubiatowo (Poland), first on November 2017 and then on December 2018. The study site is an area with hydrodynamics and lithodynamics typical of the south Baltic coast built of fine sands. The analysis is based on a differential map calculated from the bathymetric data obtained. The results show changes in the sea bottom ranging from a few to 70 centimeters. Sonar measurements were also made in 2017. The images revealed bottom ripples with an approximate height of 5–20 cm and length of 100–200 cm. The uniqueness of this research lies in the fact that at such depths there should theoretically be no significant changes at the sea bottom.

Floating tracer clustering is studied in oceanic flows that combine both a field of coherent mesoscale vortices simulated by a regional, comprehensive, eddy-resolving general circulation model and randomly modeled submesoscale velocity fields. Both fields have rotational and divergent velocity components, and depending on their relative contributions as well as on the local characteristics of the mesoscale vortices, we reported different clustering scenarios. We found that inclusion of the mesoscale vortices does not prevent clustering, but the rates and patterns of clustering become significantly modified. We also demonstrated that even when the surface velocity divergence is weak, it has to be taken into account to avoid significant errors in model predictions of the floating tracer patterns. Our approach combining dynamically constrained and random velocity fields, and the applied diagnostic methods, are proposed as standard tools for analyses and predictions of floating tracer distributions, both in observational data and general circulation models.

Vast quantities of marine debris have beached at remote islands in the western Indian Ocean such as Seychelles, but little is known about where this debris comes from. To identify these sources and temporal patterns in accumulation rate, we carried out global Lagrangian particle tracking experiments incorporating surface currents, waves, and variable windage, beaching, and sinking rates, taking into account both terrestrial (coastal populations and rivers) and marine (fisheries and shipping) sources of debris. Our results show that, whilst low-buoyancy terrestrial debris may originate from the western Indian Ocean (principally Tanzania, Comoros, and Seychelles), most terrestrial debris beaching at remote western Indian Ocean islands drifts from the eastern and northern Indian Ocean, primarily Indonesia and, to a lesser extent, India and Sri Lanka. Purse-seine fragments beaching at Seychelles are likely associated with fishing activity in the western Indian Ocean, but longline fragments may also be swept from the southeastern Indian Ocean. The entire of Seychelles is at very high risk from waste discarded from shipping routes transiting the Indian Ocean, and comparison with observations suggests that many bottles washing up on beaches may indeed originate from these routes. Our analyses indicate that marine debris accumulation at Seychelles (and the Outer Islands in particular) is likely to be strongly seasonal, peaking during February-April, and this pattern is driven by local monsoonal winds. This seasonal cycle may be amplified during positive Indian Ocean Dipole phases and El-Ni\~{n}o events. These results underline the vulnerability of small island developing states to marine plastic pollution, and are a crucial first step towards improved management of the issue. The Lagrangian trajectories used in this study are available for download, and our analyses can be rerun under different parameters using the associated scripts.

In the Arctic Ocean, semidiurnal-band processes including tides and wind-forced inertial oscillations are significant drivers of ice motion, ocean currents and shear contributing to mixing. Two years (2013-2015) of current measurements from seven moorings deployed along °E from the Laptev Sea shelf (~50 m) down the continental slope into the deep Eurasian Basin (~3900 m) are analyzed and compared with models of baroclinic tides and inertial motion to identify the primary components of semidiurnal-band current (SBC) energy in this region. The strongest SBCs, exceeding 30 cm/s, are observed during summer in the upper ~30 m throughout the mooring array. The largest upper-ocean SBC signal consists of wind-forced oscillations during the ice-free summer. Strong barotropic tidal currents are only observed on the shallow shelf. Baroclinic tidal currents, generated along the upper continental slope, can be significant. Their radiation away from source regions is governed by critical latitude effects: the S baroclinic tide (period = 12.000 h) can radiate northwards into deep water but the M (~12.421 h) baroclinic tide is confined to the continental slope. Baroclinic upper-ocean tidal currents are sensitive to varying stratification, mean flows and sea ice cover. This time-dependence of baroclinic tides complicates our ability to separate wind-forced inertial oscillations from tidal currents. Since the shear from both sources contributes to upper-ocean mixing that affects the seasonal cycle of the surface mixed layer properties, a better understanding of both inertial motion and baroclinic tides is needed for projections of mixing and ice-ocean interactions in future Arctic climate states.

El Niño-Southern Oscillation (ENSO) seasonal phase-locking behaviors simulated in 36 Coupled Model Intercomparison Project Phase 6 (CMIP6) models are evaluated for the first time by comparison with 43 CMIP5 models and observations. There are much more aborted ENSO events (simulated mature phase occurring out of the winter season) in 30 CMIP6 and 33 CMIP5 models than in observations, which indicates that the reasonable ENSO seasonal phase-locking is still a challenge to state-of-the-art climate models. Furthermore, the seasonal cycle of the zonal SST gradient along the equator can explain approximately 30% and 36% of the variance in the ENSO phase locking for CMIP5 and CMIP6, respectively. Moreover, both the spatial distribution and the phase change timing of the zonal SST gradient seasonal cycle are crucial for the ENSO seasonal phase locking. Improvement of the simulating ENSO phase-locking should be realized by focusing on the seasonal cycle of the zonal SST gradient.

Diapycnal mixing shapes the distribution of climatically-important tracers, such as heat and carbon, as these are carried by dense water masses in the ocean interior. Here, we analyze a suite of observation-based estimates of diapycnal mixing to assess its role within the Atlantic Meridional Overturning Circulation. The rate of water mass transformation in the Atlantic Ocean’s interior shows that there is a robust buoyancy increase in the North Atlantic Deep Water (NADW), with a diapycnal circulation of up to 4 Sv between 24N and 32S in the Atlantic Ocean. Moreover, tracers within the southward-flowing NADW may undergo a substantial diapycnal transfer, equivalent to hundreds of metres in the vertical. This result is confirmed with a zonally-averaged numerical model of the AMOC and indicates that tracer mixing can lead to divergent global pathways and ventilation timescales following the upwelling of tracers in the Southern Ocean. These results point to the need for a realistic mixing representation in climate models in order to understand and credibly project the ongoing climate change.

Over the last ten years, satellite and geographically constrained in situ observations largely focused on the northern hemisphere have suggested that annual phytoplankton biomass cycles in bloom-forming ocean regions cannot be fully understood from environmental properties controlling phytoplankton division rates (e.g., nutrients and light). Here, we use multi-year observations from a very large array of robotic drifting buoys in the Southern Ocean to determine key factors governing phytoplankton biomass dynamics over the annual cycle. Our analysis reveals phytoplankton blooming events occurring during periods of declining division rates, an observation that clearly highlights the importance of changing loss processes in dictating the evolution of the bloom. Bloom magnitude is found to be greatest in areas with high dissolved iron concentrations, consistent with iron being a well-established primary limiting nutrient in the Southern Ocean. Projections for expected future seasonal variations in nutrient and light availability indicate a 10% change in phytoplankton division rate may be associated with a 50% reduction in mean bloom magnitude and annual primary productivity in the Southern Ocean. Our results highlight the importance of quantifying and accounting for both changing phytoplankton division and loss processes when modeling future changes in phytoplankton bloom cycles.

Stratospheric volcanic aerosol can have major impacts on global climate. Despite a consensus among studies on an El Niño–like response in the first or second post-eruption year, the mechanisms that trigger a change in the state of El Niño-Southern Oscillation (ENSO) following volcanic eruptions are still debated. Here, we shed light on the processes that govern the ENSO response to tropical volcanic eruptions through a series of sensitivity experiments with an Earth System Model where a uniform stratospheric volcanic aerosol loading is imposed over different parts of the tropics. Three tropical mechanisms are tested: the “ocean dynamical thermostat” (ODT); the cooling of the Maritime Continent; and the cooling of tropical northern Africa (NAFR). We find that the NAFR mechanism plays the largest role, while the ODT mechanism is absent in our simulations as La Niña-like rather than El-Niño-like conditions develop following a uniform radiative forcing over the equatorial Pacific.

Natural coastal foredune systems often contain blowouts, through which beach sand is blown into the more landward dunes. Along many developed coasts, blowouts have long been considered a safety hazard, endangering the strength of the foredune as the primary sea defense. Natural blowouts have thus been actively vegetated to promote sand accumulation in the foredune. Recent studies have, however, illustrated that the cessation of sand input in the landward dunes has contributed to a reduction in biodiversity. Nowadays, the safety of coastal foredunes can be assessed with sufficient accuracy allowing for the reintroduction of blowouts. As there is little knowledge on how to optimize blowout layout, the present approach is largely ‘learning by doing’. As a result, many different layouts, varying in blowout width, plan view and orientation, have been adopted in various dune restoration projects. The aim of this study is to model the airflow through an existing man-made blowout and to validate the model results using field observations. We expect that a better understanding of airflow patterns will help in optimizing the design of future blowouts as part of dune restoration projects. The open source Computational Fluid Dynamics (CFD) package OpenFOAM was used to model wind flow through a man-made trough blowout in Dutch National Park Zuid-Kennemerland. The length of the blowout extends roughly 100 m through the foredune; its width narrows from 100 m at the seaward entrance to 20 m at its narrowest part after which it widens again. The deepest part is around 7 m above mean sea level (MSL) while the crest of the surrounding foredune is at 21 m above MSL. The blowout orientation is nearly parallel to the dominant SW wind direction and oblique with respect to the approximately N-S coast line. The field data comprises long-term (many months) observations of wind speed and direction at four locations on the blowout basin and depositional lobe. The model is able to reproduce the observed topographical steering of the wind towards the blowout normal under oblique wind approach as well as the wind-speed acceleration toward the narrowest part of the blowout. Consistent with the observations, the degree of steering and acceleration depend strongly on the wind approach angle, not on the wind speed. As a next step we envision the modeling of different blowout topographies to determine the blowout shape that potentially maximizes the sand transport toward the landward dunes.

The necessity to understand the influence of global ocean change on biota has exposed wide-ranging gaps in our knowledge of the fundamental principles that underpin marine life. Concurrently, physiological research has stagnated, in part driven by the advent and rapid evolution of molecular biological techniques, such that they now influence all lines of enquiry in biological and microbial oceanography. This dominance has led to an implicit assumption that physiology is outmoded, and advocacy that ecological and biogeochemical models can be directly informed by omics. However, the main modelling currencies continue to be biological rates and biogeochemical fluxes. Here we ask: how do we translate the wealth of information on physiological potential from omics-based studies to quantifiable physiological rates and, ultimately, to biogeochemical fluxes? Based on the trajectory of the state-of-the-art in biomedical sciences, along with case-studies from ocean sciences, we conclude that it is unlikely that omics can provide such rates in the coming decade. Thus, while physiological rates will continue to be central to providing projections of global change biology, we must revisit the metrics we rely upon. We advocate for the co-design of a new generation of rate measurements that better link the benefits of omics and physiology.