This paper presents a new sedimentary nitrogen isotope record (d15N) of a sediment core from the southeastern Arabian Sea (AS). By compiling the published nitrogen isotope data in the AS, we obtain geographically distinctive bottom-depth effects for the northern and southern AS since 35ka. After eliminating the bottom-depth bias, we observe opposite d15N trends in the Holocene between these two areas, reflecting a special coupling of denitrification to the north and N2-fixation to the south.

Beaded streams have deep elliptical pools connected by narrow runs that we show are common landforms in the continuous permafrost zone. These fluvial systems often initiate from lakes and occur predictably in headwater portions of moderately sloping watersheds. Snow capture along stream courses reduces ice thickness allowing thawed sediment to persist under most pools. Interpool thermal variability and hydrologic regimes provide important aquatic habitat and connectivity in Arctic landscapes.

We compared pCO2 data calculated from pH and alkalinity from those measured directly in a large array of temperate and tropical freshwaters. This revealed a large overestimation (up to 300%) of calculated pCO2 in the case of acidic and organic-rich waters, due to a contribution of organic acids anions to alkalinity and a lower buffering capacity of the carbonate system at acidic pH. Given the widespread distribution of acidic freshwaters, direct measurements of water pCO2 are encouraged.

This study investigates the interactions among the carbon, water and heat cycles above a maize field at the diurnal scale. We couple two land-surface schemes, corresponding to two different modelling approaches, to the same atmospheric boundary-layer (ABL) model. We find the simpler meteorological approach best reproduces the surface and upper-air observations. Finally, we show that the interaction of subsidence with ABL dynamics is key to explain the daytime atmospheric CO2 budget.

To identify site specific differences in CO2-related processes in open peatlands, we calibrated a process oriented model to fit to detailed measurements of carbon fluxes and compared the resulting parameter ranges between the sites. For most processes a common configuration could be applied. Site specific differences were identified for soil respiration coefficients, plant radiation-use efficiencies and plant storage fractions for spring regrowth.

CO2 fluxes in Funil Reservoir (FR) is driven by primary production and river inflow dynamics. Our findings suggest that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the FR is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO2 spatial variability than the in-system ecological factors.

Unmanned aerial vehicles (UAVs) equipped with optical sensors facilitate non-invasive, real-time vegetation analysis. To guarantee robust scientific analysis, protocols need to be developed and sensors must be compared to state-of-the-art instruments. Here we compare four UAV sensors (RGB, NIR, six-band, spectrometer) to evaluate their applicability for vegetation monitoring. By showing the opportunities and pitfalls of UAV-based sensing, we describe ways to gather sound scientific data.

Impacts of soil moisture on de novo monoterpene emissions from several tree species were studied. Mild drought slightly increased MT emissions, but with further progressing drought the emissions decreased to almost zero. Increases of MT emissions were explainable by increases of leaf temperature due to lowered transpirational cooling. The decrease of emissions observed when soil moisture fell below certain thresholds was parameterized, allowing considering impacts of soil moisture in models.

The observed seasonal cycles in atmospheric potential oxygen (APO) at five surface monitoring sites are compared to those inferred from the air-sea O2 fluxes of six ocean biogeochemistry models. The simulated air-sea fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM) uncertainty among 13 different ATMs. Net primary production (NPP), estimated from satellite ocean color data, is also compared to model output.

Marine DOM is known to exhibit stoichiometry depleted in N and P compared with POM, suggesting variable production and remineralization stoichiometry for C, N, and P within marine DOM cycling. We utilize marine DOM observations and an inverse tracer modeling framework to optimize DOM cycling parameters for the BEC biogeochemistry ocean model of the CESM, finding a variable stoichiometry with faster turnover of P > N > C superior to the commonly assumed Redfield stoichiometry for marine DOM.

Planktonic foraminifera are an important component of the marine carbon/carbonate cycle, yet the environmental controls on their abundances are still debated. In our study, we see larger foraminifera fluxes, particularly of heavy species, during winter when nutrients are mixed into the surface waters or during eddy mixing. Climatic factors that control mixing could therefore control the flux of planktonic foraminfera and the carbon/carbonate flux on seasonal and decadal timescales.

Emissions from fires are estimated as products of fuel load, burning efficiency, area burnt and emission factors for compounds of interest. Uncertainties in these variables lead to a wide range of estimates. We demonstrate that the probability of estimating true emissions declines strongly as the amount of information available declines. Including coarse woody debris in estimates increased uncertainty in calculations because it was the most variable contributor to fuel load.