Continuous measurement of air–water gas exchange by underwater eddy covariance Biogeosciences DOI 10.5194/bg-14-5595-2017 11 December 2017 We use the aquatic eddy covariance technique – developed first for benthic O2flux measurements – right below the air–water interface (~ 4 cm) to determine gas exchange rates and coefficients. This use of the technique is particularly useful in studies of gas exchange and its dynamics and controls. The approach can thus help reduce the recognized problem of large uncertainties linked to gas exchange estimates in traditional aquatic ecosystem studies. Read more
Reviews and syntheses: on the roles trees play in building and plumbing the critical zone Biogeosciences DOI 10.5194/bg-14-5115-2017 17 November 2017 This review represents the outcome from an invigorating workshop discussion that involved tree physiologists, geomorphologists, ecologists, geochemists, and hydrologists and developed nine hypotheses that could be tested. We argue these hypotheses point to the essence of issues we must explore if we are to understand how the natural system of the earth surface evolves, and how humans will affect its evolution. This paper will create discussion and interest both before and after publication. Read more
Global consequences of afforestation and bioenergy cultivation on ecosystem service indicators Biogeosciences DOI 10.5194/bg-14-4829-2017 3 November 2017 Many climate change mitigation scenarios require negative emissions from land management. However, environmental side effects are often not considered. Here, we use projections of future land use from two land-use models as input to a vegetation model. We show that carbon removal via bioenergy production or forest maintenance and expansion affect a range of ecosystem functions. Largest impacts are found for crop production, nitrogen losses, and emissions of biogenic volatile organic compounds. Read more
Vertical segregation among pathways mediating nitrogen loss (N2 and N2O production) across the oxygen gradient in a coastal upwelling ecosystem Biogeosciences DOI 10.5194/bg-14-4795-2017 26 October 2017 This investigation characterizes the variability of pathways involved in N loss in the water column over the continental shelf off central Chile during the development of the upwelling season. Our results highlight the links between several pathways involved in N removal, and considering the extreme variation in oxygen observed could help to understand the ecological and biogeochemical implications due to global warming when intensification and/or expansion of the oceanic OMZs are projected. Read more
Expansion of oil palm and other cash crops causes an increase of the land surface temperature in the Jambi province in Indonesia Biogeosciences DOI 10.5194/bg-14-4619-2017 25 October 2017 From the analysis of MODIS and Landsat satellite data of the Jambi province in Indonesia, this first study on the effects of oil palm expansion on the surface temperature in Indonesia shows shows a local and regional warming effect caused by the expansion of oil palm plantations and other cash or tree crops between 2000 and 2015. The observed warming effects may affect ecosystem services, reduce water availabilty in the dry period and increase the vulnerability to fires in the province. Read more
Reviews and syntheses: Systematic Earth observations for use in terrestrial carbon cycle data assimilation systems Biogeosciences DOI 10.5194/bg-14-3401-2017 19 July 2017 This paper briefly reviews data assimilation techniques in carbon cycle data assimilation and the requirements of data assimilation systems on observations. We provide a non-exhaustive overview of current observations and their uncertainties for use in terrestrial carbon cycle data assimilation, focussing on relevant space-based observations. Read more
On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic Biogeosciences DOI 10.5194/bg-14-3337-2017 13 July 2017 We find that a big portion of the phytoplankton, zooplankton, and detrital organic matter produced near the northern African coast is laterally transported towards the open North Atlantic. This offshore flux sustains a relevant part of the biological activity in the open sea and reaches as far as the middle of the North Atlantic. Our results, obtained with a state-of-the-art model, highlight the fundamental role of the narrow but productive coastal ocean in sustaining global marine life. Read more
Divergence of seafloor elevation and sea level rise in coral reef ecosystems Biogeosciences DOI 10.5194/bg-14-1739-2017 20 April 2017 We report regional-scale erosion of coral reef ecosystems in the Atlantic, Caribbean, and Pacific oceans determined by measuring changes in seafloor elevation. The magnitude of seafloor elevation loss has increased local sea level rise, causing water depths not predicted until near 2100, placing coastal communities at elevated and accelerating risk from hazards such as waves, storms, and tsunamis. Our results have broad implications for coastal resource and safety management. Read more
Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese Biogeosciences DOI 10.5194/bg-14-1123-2017 9 March 2017 We ran a global ocean model to understand manganese (Mn), a biologically essential element. Our model shows that (i) in the deep ocean, dissolved [Mn] is mostly homogeneous ca. 0.10–0.15 nM. The model reproduces this with a threshold on MnO2 of 25 pM, suggesting a minimal particle concentration is needed before aggregation and removal become efficient. (ii) The observed distinct hydrothermal signals are produced by assuming both a strong source and a strong removal of Mn near hydrothermal vents. Read more
Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef Biogeosciences DOI 10.5194/bg-13-6441-2016 7 December 2016 Marine biogeochemical models are often used to understand water quality, nutrient and blue-carbon dynamics at scales that range from estuaries and bays, through to the global ocean. We introduce a new methodology allowing for the assimilation of observed remote sensing reflectances, avoiding the need to use empirically derived chlorophyll-a concentrations. This method opens up the possibility to assimilate of reflectances from a variety of missions and potentially non-satellite platforms. Read more