Abstracted/indexed

The Indian Ocean-rim hosts many of the underdeveloped and emerging economies that depend on the ocean resources for the livelihood of the millions. Operational ocean information services cater to the requirements of managers and end-users to efficiently harness resources, and ensure safety. This paper reviews existing tools, and explores the ongoing research that has potential to convert the findings into operational services in near-to-mid term.

This work enunciates the possibility of kerogen oxidation as a major driver of atmospheric CO₂ increase in the wake of glacial episodes. This hypothesis is substantiated by several lines of independent evidence synthesized in this contribution. The author hypothesizes that the deglaciation of kerogen-rich lithologies in western Canada contributed majorly to the characteristic deglacial increase in atmospheric CO₂.

Sediments in oxygen-depleted ocean areas release high amounts of phosphorus, feeding algae that consume oxygen upon degradation, leading to further phosphorus release. Oxygenation is thought to trap phosphorus in the sediment and break this feedback. We studied the sediment phosphorus cycle in a previously anoxic area after an inflow of oxic water. Surprisingly, the sediment phosphorus release increased, showing that feedbacks between phosphorus release and oxygen depletion can be hard to break.

Expanding shrubs in the Arctic are changing snowpacks into a mixture of snow, impurities and buried branches. Snow is a translucent medium into which light penetrates and gets partly absorbed by branches. Thus, branches heat up and modify snow properties. Measurements taken in snowpacks with shrubs showed that buried branches increase light absorption, but only locally. This is supported by observations of localized melting and pockets of large crystals forming a few centimeters around branches.

Bioaerosols in the atmosphere over the Amazon rain forest were analyzed by molecular biological staining and microscopy. Eukaryotic, bacterial and archaeal aerosols were quantified in time series and altitude profiles exhibiting clear differences in number concentrations and vertical distributions. Our results provide insights into the sources and dispersion of different Amazonian bioaerosol types as a basis for a better understanding of biosphere-atmosphere interactions.

Upwelling of nutrient-rich deep waters to the surface make Eastern Boundary upwelling systems hotspots of marine productivity. This leads to sub-surface oxygen-depletion and transformation of bio-available nitrogen into inert N₂. Here we quantify nitrogen loss processes following a simulated deep-water upwelling. Denitrification was the dominant process and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.

This study integrates numerical simulations (using a multi-spectral optical model) with in-situ measurements of floats and remotely sensed observations from satellites. It aims at improving our current understanding of the impact that different constituents (such as pure water, colored dissolved organic matter, detritus and phytoplankton) have on the in-water light propagation.

The Gulf of Mexico deep waters are relatively poor in phytoplankton biomass due to low levels of nutrient in the upper layers. Using modelling techniques, we find that the long-living anticyclonic Loop Current Eddies that are shed episodically from the Yucatan Channel strongly shape the distribution of phytoplanktons and, more importantly, stimulate their growth. This results from the contribution of multiple mechanisms of physical-biogeochemical interactions discussed in this study.

The hydro-biogeochemical model (CNMM-DNDC) is improved by incorporating a soil thermal module to simulate the soil thermal regime in the presence of freeze-thaw cycles. The modified model was validated at a seasonally frozen catchment with typical alpine ecosystems (wetlands, meadows and forests). The simulated aggregate emissions of methane and nitrous oxide were significantly reduced due to wetland degradation and were dominated by a reduction in methane emissions.

Increasing soil organic carbon (SOC) stocks is beneficial for climate change mitigation and food security. One way to enhance SOC stocks is to increase carbon inputs to the soil. We estimated the amount of carbon inputs required to reach a 4 ‰ annual increase of SOC stocks in 14 long-term agricultural experiments around Europe. We found that annual carbon inputs should increase by 43 % under current temperature conditions, by 54 % for a 1 °C warming scenario and by 120 % for a 5 °C warming scenario.

Climate change can change vegetation characteristics in grasslands with a potential impact on forage quality, use by ruminants, and in turn greenhouse gas emissions such as enteric methane. Using controlled conditions mimicking a future climatic scenario, we show that forage quality and ruminant digestion are affected in opposite ways by elevated atmospheric CO₂ and an extreme event (heat wave, severe drought), indicating that different factors of climate change have to be considered together.

CO₂ concentrations in small rivers are mainly controlled by lateral soil CO₂ input, while the decomposition of organic carbon controls the CO₂ variation in large rivers. CO₂ fluxes in the wet season, compared to that in the dry season, are 2-fold larger due to high CO₂ concentration and turbulence caused by high flow velocity. The absence of high CO₂ fluxes in small rivers could be associated with the depletion effect caused by abundant precipitation under the subtropical monsoon climate.

Bogs of Northern Eurasia represent a major type of peatland ecosystem and contain vast amounts of carbon, but carbon balance monitoring studies on bogs remain scarce. The current project explores six years of carbon balance data obtained using the state-of-art eddy-covariance technique at a Finnish bog Siikaneva. The results reveal relatively low interannual variability indicative of ecosystem resilience to both cool and hot summers, and provides new insight into the seasonal course of C fluxes.

Remote sensing has played an important role in studying land surface processes. Geostationary satellites such as the GOES-R series can observe the earth every 5–15 minutes providing us with more observations than widely used polar orbiting satellites. Here, we outline current efforts utilizing geostationary observations in environmental science and look towards the future of GOES observations in the carbon cycle, ecosystem disturbance, and other areas of application in environmental science.

Biological rock crusts (BRCs) are ubiquitous features of rock surfaces in deserts composed of slow-growing microorganisms. Many BRCs are assumed to be thousands of years old, but precise dating has so far been impossible. Using a combination of archaeological, microbial and geological evidence, we calculated the aga of a BRC from a Byzantine archaeological site in the Central Negev Desert, Israel. The BRC growth rates were estimated at 0.06–0.35 mm 1000 years; faster than previously suggested.

Amphistegina lobifera (Foraminifera) has colonized the Mediterranean through the Suez Canal, often forming thick sediments altering the invaded environments. Little is known about post mortem fate of its shells, so I investigated their turnover in the rhizosphere of the dominant Mediterranean seagrass. Most of them were bioeroded, likely by cyanobacteria and algae, not fungi occurring in the seagrass roots. Bioerosion may counterbalance accumulation of A. lobifera shells in the seabed substrate.

In this study we analyse surface ocean dimethylsulfide (DMS) concentration and flux to the atmosphere from four CMIP6 Earth System Models over the historical and ssp585 simulations. Our analysis of contemporary (1980–2009) climatologies shows that models better reproduce observations in mid to high latitudes. The models disagree on the sign of the trend of the global DMS flux from 1980 onwards. The models agree on a positive trend of DMS over polar latitudes following sea-ice retreat dynamics.

Coccolithophores are important unicellular algae with a calcium carbonate covering that might be affected by ongoing changes in the ocean due to absorption of CO₂, warming, and melting of glaciers. We used the Southern Patagonian Fjords as a natural laboratory, where chemical conditions are naturally highly variable. One variant of a widespread coccolithophore species can tolerate these conditions, suggesting it is highly adaptable, while others were excluded, suggesting they are less adaptable.

Soil organic matter (SOM) is essential for the health of soils and the accumulation of SOM helps removal of CO₂ from the atmosphere. Here we present the result of the continued development of a mathematical model that simulates SOM and its measurable fractions. In this study, we simulated serval grassland sites in the U.S. and the model generally captured the carbon and nitrogen amounts in SOM and their distribution between the measurable fractions throughout the entire soil profile.

It remains unclear what controls carbon burial in marine sediments. Thus, we combined model and data analyses to identify patterns of organic matter reactivity at the seafloor on a large-scale. We found large spatial variability on organic matter reactivity, which results from complex regional environmental factors. Based on that, we estimated rates of carbon and nutrient recycling within sediments. Our results are essential to improve predictions of future changes on carbon cycling and climate.

The Arctic Ocean receive enormous amounts of river water, which is rich in dissolved organic matter (tDOM) and an important component of the Arctic carbon cycle. Our analysis shows that mixing of three major freshwater sources is the main factor that regulates the distribution of tDOM concentrations in the Siberian shelf seas. In this context, the formation and melting of the land-fast ice in the Laptev Sea and the peak spring discharge of the Lena River are of particular importance.

We quantify one form of uncertainty in modeled 21st-century changes in phytoplankton growth. The supply of nutrients from deep to surface waters decreases in the warmer future ocean, but the effect on phytoplankton growth also depends on changes in available light, how much light and nutrient the plankton need, and how fast they can grow. These phytoplankton properties can be summarized as a biological timescale: when it is short, future growth decreases twice as much as when it is long.

Diagnostics of the latest generation earth system models reveal the ocean will continue to absorb a large fraction of the anthropogenic carbon released to the atmosphere in the next century, with the Atlantic Ocean storing a large amount of this carbon relative to its size. The ability of the ocean to absorb carbon will reduce in the future as the ocean warms and acidifies. This reduction is larger in the Atlantic Ocean due to a weakening of the meridional overturning with changes in climate.

Shrub and sedge plant functional types (PFTs) were incorporated in the land surface component of the Canadian Earth System Model to improve representation of Arctic tundra ecosystems. Evaluated against 14 years of non-winter measurements, the magnitude and seasonality of carbon dioxide and energy fluxes at a Canadian dwarf-shrub tundra site were better captured by the shrub PFTs than by previously used grass and tree PFTs. Model simulations showed the tundra site to be an annual net CO₂ source.

Model uncertainty dominates the spread in terrestrial carbon cycle predictions. Efforts to reduce it typically involve adding processes, thereby increasing model complexity. However, if and how model performance scales with complexity is unclear. Using a suite of 16 structurally distinct carbon cycle models, we find that increased complexity only improves skill if parameters are adequately informed. Otherwise, it can degrade skill and an intermediate complexity model is optimal.

We evaluated a new diffusive soil probe integrated with high-resolution gas analyzers to measure soil gases in real-time at a centimeter-scale. Using columns with simple silica and soil, we captured changes in carbon dioxide (CO2), volatile organic compounds (VOCs), and nitrous oxide (N2O) with its isotopes to distinguish potential nutrient sources and microbial metabolism. This approach will advance the use of soil gases as important signals to understand and monitor soil fertility and health.

The motion of trees in the wind is related to wind damage risk and surface-atmosphere energy exchange. We collated all tree motion data and summarized the main patterns. We confirmed that the fundamental frequency of tree sway is related to tree height. We found that the motion of trees in conifer forests, the most studied system, is somewhat distinct from that of open-grown trees and broadleaf forests. We also found that no additional damping or amplification process emerge at high wind speeds.