The role of coastal wetlands as natural ‘blue carbon’ sinks may be counter‐acted by emissions of methane (CH4) and nitrous oxide (N2O). Site‐specific fluxes of these two potent greenhouse gases from coastal wetlands show high spatial and temporal variability , making global estimates sensitive to statistical assumptions and uncertainties. Here, we review the magnitude of CH4 and N2O fluxes from mangroves

The contribution of continental shelves to the marine carbon cycle is still poorly understood. Their preindustrial state is, for one, essentially unknown, which strongly limits the quantitative assessment of their anthropogenic perturbation. To date, approaches developed to investigate and quantify carbon fluxes on continental shelves have strongly simplified their physical and biogeochemical features

The response of tropical ecosystems to elevated carbon dioxide (CO2) remains a critical uncertainty in projections of future climate. Here, we investigate how leaf trait plasticity in response to elevated CO2 alters projections of tropical forest competitive dynamics and functioning. We use vegetation demographic model simulations to quantify how plasticity in leaf mass per area and leaf carbon to

Earth's carbon cycle maintains a stable climate and biosphere on geological timescales. Feedbacks regulate the size of the surface carbon reservoir, and on million‐year timescales the carbon cycle must be in steady state. A major question about the early Earth is whether carbon was cycled through the surface reservoir more quickly or slowly than it is today. The answer to this question holds important

Molybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea‐salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion

As climate change accelerates, positive feedback loops could establish between atmospheric warming and increasing greenhouse gas (GHG) emissions from natural ecosystems. Of particular interest are high‐latitude environments, many of which contain large stores of organic carbon and have experienced decades of accelerated warming. Freshwater ecosystems situated in carbon‐rich Arctic landscapes are predicted

The 13C/12C of dissolved inorganic carbon (δ13CDIC) carries valuable information on ocean biological C‐cycling, air‐sea CO2 exchange, and circulation. Paleo‐reconstructions of oceanic 13C from sediment cores provide key insights into past as changes in these three drivers. As a step towards full inclusion of 13C in the next generation of Earth system models, we implemented 13C‐cycling in a 1° lateral

Export of Particulate Organic Carbon (POC) is mainly driven by gravitational sinking. Thus, traditionally, it is thought that larger, faster‐sinking particles make up most of the POC export flux. However, this need not be the case for particles whose sinking speeds are comparable to the vertical velocities of a dynamic flow field that can influence the descent rate of particles. Particles with different

Global Earth system model simulations of ocean carbon export flux are commonly interpreted only at a fixed depth horizon of 100 m, despite the fact that the maximum annual mixed layer depth (MLDmax) is a more appropriate depth horizon to evaluate export‐driven carbon sequestration. We compare particulate organic carbon (POC) flux and export efficiency (e‐ratio) evaluated at both the MLDmax and 100‐m

Phytoplankton photosynthesize in surface waters, exporting organic carbon to depth through the biological pump. Quantifying productivity and the export of carbon is important to understanding the global carbon cycle and predicting its future changes. An issue in quantifying rates is that the many existing methods are not all equivalent, making comparisons between studies using different methods challenging

Seasonal oxygen structure and utilization in the Sargasso Sea are characterized using nine profiling floats with oxygen sensors (years 2005‐2008), deployed in an Eighteen Degree Water (EDW) experiment (CLIMODE). During autumn‐winter when the mixed layer is deepening, oxygen increases from the surface to the base of the EDW at 400 m. During spring‐summer, oxygen decreases except between the seasonal

The air‐water exchange of trace gases such as CO2 is usually parameterized in terms of a gas transfer velocity, which can be derived from direct measurements of the air‐sea gas flux. The transfer velocity of poorly soluble gases is driven by near‐surface ocean turbulence, which may be enhanced or suppressed by the presence of sea ice. A lack of measurements means that air‐sea fluxes in polar regions

An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11°S and 12°S. Each transect extends from the shelf to the upper slope (∼1,000 m) and dissects the permanently anoxic waters between ∼200 and 500 m water depth. BSi burial (2,100 mmol m−2 yr−1) and recycling fluxes (3,300 mmol m−2 yr−1) were highest on the shelf with mean preservation efficiencies

The global socio‐economic and agricultural expansion is accompanied by large inputs of nitrogen (N) and phosphorus (P) on land and by a serious alteration of the water cycle and water quality. The Mediterranean basin represents a paradigmatic region to study the entangled nutrient and water challenges because the region, where many of the world's climatic and socio‐economic gradients are present, is

Spatial analysis in earth sciences is often based on the concept of spatial autocorrelation, expressed by W. Tobler as the first law of geography: “everything is related to everything else, but near things are more related than distant things”. Here, we show that sub‐surface soil properties in permafrost tundra terrain exhibit tremendous spatial variability. We describe the sub‐surface variability

Glaciers and ice sheets cover over 10 % of Earth's land surface area and store a globally significant amount of dissolved organic matter (DOM), which is highly bioavailable when exported to proglacial environments. Recent rapid glacier mass loss is hypothesized to have increased fluxes of DOM from these environments, yet the molecular composition of glacially derived DOM has only been studied for a

Nitrous oxide (N2O), a potent greenhouse gas, is produced disproportionately in marine oxygen deficient zones (ODZs). To quantify spatiotemporal variation in N2O cycling in an ODZ, we analyzed N2O concentration and isotopologues along a transect through the eastern tropical North Pacific (ETNP). At several stations along this transect, N2O concentrations reached a near surface maximum that exceeded

Peatlands play an important role as carbon pools, storing a third of the world's soil carbon. However, peatlands in Southeast Asia have suffered from depletion due to economic pressure and the demand for natural resources, often caused by land use changes and fires. Usually, land preparation requires drainage and fires, resulting in major greenhouse gas (GHG) emissions into the atmosphere. In this

We report in situ rates of gross oxygen production (GOP), community respiration (R), and net community production (NCP) in the North Pacific Subtropical Gyre derived from mixed layer O2/Ar measurements. The measurements were conducted between November 2013 and January 2019 at the site of the Hawaii Ocean Time‐series program. Biological O2 concentration anomalies in the mixed layer showed a consistent

No abstract is available for this article.

No abstract is available for this article.

We present a decade of dissolved and particulate silica concentrations within five biological “hot spots” in the Pacific Arctic Region (PAR) and the first measurements of both biogenic silica production rates (ρSi) and the kinetics of silicon utilization from a period of four years at the same sites. The “hot spots” were located within the Bering and Chukchi Seas and identified as part of the Distributed

To examine seasonal and regional variabilities in metabolic status and the coupling of net community production (NCP) and air–sea CO2 fluxes in the western Arctic Ocean, we collected underway measurements of surface O2/Ar and partial pressure of CO2 (pCO2) in the summers of 2016 and 2018. With a box‐model, we demonstrate that accounting for local sea ice history (in addition to wind history) is important

Approximately half of global primary production occurs in the oceans. While the large‐scale variability in net primary production (NPP) has been extensively studied, ocean gross primary production (GPP) has thus far received less attention. In this study, we derived two satellite‐based GPP models by training machine‐learning algorithm (Random Forest) with light‐dark bottle incubations (GPPLD) and the

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile

The concentrations of weathering‐derived solutes in rivers and their covariance with discharge are thought to reflect reactive‐transport processes in hillslopes and to reveal the sensitivity of solute fluxes to climatic change. It is expected that discharge‐driven changes in water transit times play some role in setting concentration‐discharge (C‐Q) relationships, but knowledge gaps remain. To explore

Corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production dominate Midwestern U.S. agriculture and impact the regional carbon and nitrogen cycles. Sustaining soil carbon is important for corn‐soybean production (CS); however, quantifying soil carbon changes requires long‐term field measurements and/or model simulations. In this study, changes in soil organic (SOC), inorganic (SIC), and total

We estimate preformed ocean phosphate, nitrate, oxygen, silicate, and alkalinity by combining a reconstruction of ventilation pathways in the ocean interior with estimates of submixed layer properties. These new preformed property estimates are intended to aid biogeochemical cycling studies and validation of modeled preformed property distributions and are available online. Analyses of net property

Soil nitrogen (N) transformations, which regulate soil N availability, are important for ecosystem productivity and other functions. Nitrogen deposition influences soil N transformations, but it remains unclear how soil N transformations, especially microbial N immobilization, change with different N deposition rates. In this study, we compiled a global data set of gross N mineralization, nitrification

The seasonal cycle represents one of the largest signals of dissolved inorganic carbon (DIC) in the ocean, yet these seasonal variations are not well established at a global scale. Here, we present the Mapped Observation‐Based Oceanic DIC (MOBO‐DIC) product, a monthly DIC climatology developed based on the DIC measurements from GLODAPv2.2019 and a two‐step neural network method to interpolate and map

In this study we evaluate the benthic fluxes of silicic acid along the West Antarctic Peninsula (WAP). Silicic acid (DSi) is one of the macronutrients essential in fuelling biological hot spots of diatom‐dominated primary production along the WAP. Here we measure the concentration and stable silicon isotopic composition of DSi in porewater profiles, biogenic silica content (BSi), and diatom abundance

Glaciated environments have been highlighted as important sources of bioavailable nutrients, with inputs of glacial meltwater potentially influencing productivity in downstream ecosystems. However, it is currently unclear how riverine nutrient concentrations vary across a spectrum of glacial cover, making it challenging to accurately predict how terrestrial fluxes will change with continued glacial

Variability in greenhouse gas emissions from reservoirs creates uncertainty in global estimates of C emissions from reservoirs. This study examines the temporal and spatial variability in CO2 and CH4 surface water concentrations and diffusive fluxes from an Amazonian reservoir using an original data set combining both a high temporal (1 central site × 22 years) and spatial (44 sites × 1 season) resolution

Two experiments were performed during the wet and dry seasons to quantify dissolved carbon dynamics and fluxes in the Shark River, a tidal estuary flowing through the largest contiguous mangrove forest in North America (Everglades National Park, Florida, USA). During these experiments, between 80% and 87% of the total dissolved carbon pool consisted of inorganic carbon (DIC). Carbon inputs from mangroves

Dissolved organic matter (DOM) acts as an important biogeochemical component of aquatic ecosystems that controls nutrient cycling, influences water quality, and links terrestrial and oceanic carbon pools, yet long‐term studies of how changing environmental drivers alter its abundance and composition are rare. Using a 10‐year, spatially explicit data set from Everglades National Park, a globally significant

Marine oxygen deficient zones are dynamic areas of microbial nitrogen cycling. Nitrification, the microbial oxidation of ammonia to nitrate, plays multiple roles in the biogeochemistry of these regions, including production of the greenhouse gas nitrous oxide (N2O). We present here the results of two oceanographic cruises investigating nitrification, nitrifying microorganisms, and N2O production and

The net balance between photosynthesis and respiration in the surface ocean is a key regulator of ocean‐atmosphere carbon dioxide (CO2) partitioning, and by extension, Earth's climate. The slight excess of photosynthesis over community respiration in sunlit waters, known as net community production (NCP), sets the upper bound on the sequestration of carbon via biologically mediated export. Prevailing

The Mackenzie River Basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, but the spatial variability in OC sources transported by its different tributaries is still unclear. Here we

Recent work demonstrates extensive nutrient exports from outlet glaciers of the Greenland Ice Sheet. In comparison, nutrient exports are poorly defined for deglaciated watersheds that were exposed during ice retreat and retain reactive comminuted glacial sediments. Nutrient exports from deglaciated watersheds may differ from glacial watersheds due to their longer exposure times, more mature chemical

Variability in climate exerts a strong influence on vegetation productivity (gross primary productivity; GPP), and therefore has a large impact on the land carbon sink. However, no direct observations of global GPP exist, and estimates rely on models that are constrained by observations at various spatial and temporal scales. Here, we assess the consistency in GPP from global products which extend

Displaying Nitrogen (N) indicators on a global grid poses unique opportunities to quantify environmental impacts from N application in different world regions under a variety of conditions. Such calculations require the use of maps showing the geo‐spatial distribution of crop production. Although there are several crop maps in the scientific literature to choose from, the consequences of this choice

Stream networks transport and emit substantial volumes of carbon dioxide (CO2) into the atmosphere. We gathered open monitoring data from streams in three Scandinavian countries and estimated CO2 partial pressure (pCO2) at 2,298 sites. Most of the sites (87%) were supersaturated when averaged across the year with an overall mean pCO2 of 1,464 μatm (range: 17–15,646). Using remote sensing data, we modeled

Biomass burning, including fires, has been identified as the largest source of primary fine carbonaceous particles in the troposphere and one of the major drivers of global carbon (C) cycle, cloud properties, and climate. Most of the global C emissions happen in the Pantropic region. Modeling estimates suggest an increase in Mexican fire frequencies, intensity, and C emission to the atmosphere. However

Biological processes in Southern Ocean surface waters have widespread impacts on global productivity and oceanic CO2 storage. Here, we demonstrate that biological calcification in the Southern Ocean exerts a strong control on the global distribution of alkalinity. The signature of Southern Ocean calcification is evident in observations as a depletion of potential alkalinity within portions of Subantarctic

Dissolved organic nitrogen (DON) is the dominant form of fixed nitrogen in most low and middle latitude ocean surface waters. Here, we report measurements of DON isotopic composition (δ15N) from the west South China Sea (SCS), with the goal of providing new insight into DON cycling. The concentration of DON in the surface ocean is correlated (r = 0.70, p < 0.0001) with chlorophyll a concentration,

Drylands occupy nearly 40% of the land surface and comprise a globally significant carbon reservoir. Dryland‐atmosphere carbon exchange may regulate interannual variability in atmospheric CO2. Quantifying soil respiration rates in these environments is often complicated by the presence of calcium carbonates, which are a common feature of dryland soils. We show with high‐precision O2 measurements in

This review provides a synthesis of what is currently known about the natural and anthropogenic fluxes of fluorine on Earth, offering context for an evaluation of the growing environmental impact of human‐induced F mobilization and use. The largest flux of F at the Earth's surface derives from the mobilization of F during chemical (2.2 Tg F/yr (where 1 Tg = 1012 g) and mechanical (7 Tg F/yr) weathering

A potential strategy for mitigating nitrous oxide (N2O) emissions from permanent grasslands is the partial substitution of fertilizer nitrogen (Nfert) with symbiotically fixed nitrogen (Nsymb) from legumes. The input of Nsymb reduces the energy costs of producing fertilizer and provides a supply of nitrogen (N) for plants that is more synchronous to plant demand than occasional fertilizer applications

Increasing fire severity and frequency may stress ecosystems also impacted by climate change. We studied the physical limitations to regeneration after fire in an ecosystem that already experiences high summer temperatures and drought and is therefore a possible analog of the future. We compared soil respiration as an indicator of microbial activity in burned and unburned forest soils in central Texas

Human activities have caused considerable perturbations of the nitrogen (N) cycle, leading to a ~20% increase in the concentration of atmospheric nitrous oxide (N2O) since the preindustrial era. While substantial efforts have been made to quantify global and regional N2O emissions from cropland, there is large uncertainty regarding how climate change and variability have altered net N2O fluxes at annual

We present dissolved and total dissolvable trace elements for spring and summer cruises in 2010 in the high latitude North Atlantic. Surface and full depth data are provided for Al, Cd, Co, Cu, Mn, Ni, Pb, Zn in the Iceland and Irminger Basins, and consequences of biological uptake and inputs by the spring Eyjafjallajökull volcanic eruption are assessed. Ash from Eyjafjallajökull resulted in pronounced

No abstract is available for this article.

The Southern Ocean hosts complex connections between ocean physics, chemistry, and biology. Changes in these connections are hypothesized to be responsible for significant alterations of ocean biogeochemistry and carbon storage both on glacial‐interglacial timescales and in the future due to anthropogenic forcing. Isotopes of thorium (230Th and 232Th) and protactinium (231Pa) have been widely applied

The loss of carbon from soils to the atmosphere resulting from climate change is projected to be large, but these projections exhibit significant uncertainty, largely due to insufficient knowledge of the patterns and controls of the temperature sensitivity of soil microbial respiration. Here we synthesized data from 52 soil incubation studies across the Northern Hemisphere to assess the spatial patterns

Tidal flats form around the estuarine and coastal zone by continuous terrigenous sediment transport and deposition processes. Now a large body of published carbon research work frame within the vegetated area (mangrove forests, sea grass bed, and salt marshes). Nonvegetated tidal flats, which are characterized by predominantly silts and clays sediment, were generally impressed with low carbon stock

We developed vertically resolved soil biogeochemistry (carbon and nitrogen) module and implemented it into a land surface model, ISAM. The model captures the vertical heterogeneity of the northern high latitudes permafrost soil organic carbon (SOC). We also implemented Δ14C to estimate SOC turnover time, a critical determinant of SOC stocks, sequestration potential, and the carbon cycle feedback under

Methane emissions from natural wetlands tend to increase with temperature and therefore may lead to a positive feedback under future climate change. However, their temperature response includes confounding factors and appears to differ on different time scales. Observed methane emissions depend strongly on temperature on a seasonal basis, but if the annual mean emissions are compared between sites

Sea ice acts as an iron (Fe) reservoir in the Southern Ocean (SO) where primary productivity is largely Fe limited. The mechanisms leading to Fe enrichment in sea ice result from the combination of poorly understood and largely unexplored physical and biological processes. We analyze the biogeochemical impacts of three plausible idealized formulations of dissolved Fe (DFe) incorporation into sea ice

In this “Grand Challenges” paper, we review how the carbon isotopic composition of atmospheric CO2 has changed since the Industrial Revolution due to human activities and their influence on the natural carbon cycle, and we provide new estimates of possible future changes for a range of scenarios. Emissions of CO2 from fossil fuel combustion and land use change reduce the ratio of 13C/12C in atmospheric

Across temperate North America, interannual variability (IAV) in gross primary production (GPP) and net ecosystem exchange (NEE) and their relationship with environmental drivers are poorly understood. Here, we examine IAV in GPP and NEE and their relationship to environmental drivers using two state‐of‐the‐science flux products: NEE constrained by surface and space‐based atmospheric CO2 measurements