The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

Interpretation of CFC-Datasets in Wedell Sea

The aim of this thesis is to generate a circulation scheme of the deep water masses of the Weddell Sea with the primary objective to estimate production rates of different sources of these water masses using chlorofluorocarbon (CFC) data. Repeated observations of CFC for a section along the Prime Meridian from Antarctica (70°S) to approximately 50°S are presented for the period 1984 - 1998. In addition CFC data from the Weddell Sea section (Kapp Norvegia - Joinville Island) are considered. For various CFC features at this sections CFC time series have been generated, in particular for two deep cores of CFC-11 maxima adjoining the southern and northern margins of the Weddell Basin and elevated CFC concentrations over the Middle Atlantic Ridge. A new method of analyzing such CFC data has been developed. The outcome of this approach is the best fit of the age distribution, i.e. the fraction and the age of recently ventilated water. In contrast to previous methods more information about the age structure and a better error estimation could be derived. The convolution of the CFC and the velocity field results in the CFC transport through the section in this cores. The ratio of this value and the CFC surface concentration at the time of the water mass formation is an estimation of the transport of recently ventilated water within the core. Applying this to the deep cores at both sections a circulation scheme of the deep recently ventilated water could be estimated. From this scheme the production rates of the source in the western Weddell Sea and east of it (off Amery Ice Shelf) have been derived. Furthermore, the transport of the ventilated water of the mid-depth core has given an estimation of the productivity of the northern Weddell Sea. The comparison of these three sources has shown a surprising result: The production rates of all sources are in the same range (2.1±0.8 Sv western Weddell Sea; 2.4±0.8 Sv Amery Ice Shelf, about 3 Sv northern Weddell Sea)

Interpretation von FCKW-Datensätzen im Weddellmeer

The aim of this thesis is to generate a circulation scheme of the deep water masses of the Weddell Sea with the primary objective to estimate production rates of different sources of these water masses using chlorofluorocarbon (CFC) data. Repeated observations of CFC for a section along the Prime Meridian from Antarctica (70°S) to approximately 50°S are presented for the period 1984 - 1998. In addition CFC data from the Weddell Sea section (Kapp Norvegia - Joinville Island) are considered. For various CFC features at this sections CFC time series have been generated, in particular for two deep cores of CFC-11 maxima adjoining the southern and northern margins of the Weddell Basin and elevated CFC concentrations over the Middle Atlantic Ridge. A new method of analyzing such CFC data has been developed. The outcome of this approach is the best fit of the age distribution, i.e. the fraction and the age of recently ventilated water. In contrast to previous methods more information about the age structure and a better error estimation could be derived. The convolution of the CFC and the velocity field results in the CFC transport through the section in this cores. The ratio of this value and the CFC surface concentration at the time of the water mass formation is an estimation of the transport of recently ventilated water within the core. Applying this to the deep cores at both sections a circulation scheme of the deep recently ventilated water could be estimated. From this scheme the production rates of the source in the western Weddell Sea and east of it (off Amery Ice Shelf) have been derived. Furthermore, the transport of the ventilated water of the mid-depth core has given an estimation of the productivity of the northern Weddell Sea. The comparison of these three sources has shown a surprising result: The production rates of all sources are in the same range (2.1±0.8 Sv western Weddell Sea; 2.4±0.8 Sv Amery Ice Shelf, about 3 Sv northern Weddell Sea)

Interpretation von FCKW-Daten im Weddellmeer

The aim of this thesis is to generate a circulation scheme of the deep water masses of the Weddell Sea with the primary objective to estimate production rates of different sources of these water masses using chlorofluorocarbon (CFC) data. Repeated observations of CFC for a section along the Prime Meridian from Antarctica (70°S) to approximately 50°S are presented for the period 1984 - 1998. In addition CFC data from the Weddell Sea section (Kapp Norvegia - Joinville Island) are considered. For various CFC features at this sections CFC time series have been generated, in particular for two deep cores of CFC-11 maxima adjoining the southern and northern margins of the Weddell Basin and elevated CFC concentrations over the Middle Atlantic Ridge. A new method of analyzing such CFC data has been developed. The outcome of this approach is the best fit of the age distribution, i.e. the fraction and the age of recently ventilated water. In contrast to previous methods more information about the age structure and a better error estimation could be derived. The convolution of the CFC and the velocity field results in the CFC transport through the section in this cores. The ratio of this value and the CFC surface concentration at the time of the water mass formation is an estimation of the transport of recently ventilated water within the core. Applying this to the deep cores at both sections a circulation scheme of the deep recently ventilated water could be estimated. From this scheme the production rates of the source in the western Weddell Sea and east of it (off Amery Ice Shelf) have been derived. Furthermore, the transport of the ventilated water of the mid-depth core has given an estimation of the productivity of the northern Weddell Sea. The comparison of these three sources has shown a surprising result: The production rates of all sources are in the same range (2.1±0.8 Sv western Weddell Sea; 2.4±0.8 Sv Amery Ice Shelf, about 3 Sv northern Weddell Sea)

Towards an Hybrid Antarctic Float Observation System (HAFOS)

The ARGO system is expected to become the backbone of a global ocean observing system. However, it can not be easily extended into polar oceans, since the floats have to return to the sea surface to be located and to transmit the measured data. Since location and data transmission under the ice is only possible by acoustic means, an observation system in the deep polar oceans requires the combination of different technologies. The envisioned system comprises ice avoiding profiling subsurface floats which are acoustically ranged by RAFOS technology. In a first step they transmit the recorded data only when they are able to reach open water in real-time, in a second phase, they provide delayed mode data transfer during the ice-free season. Acoustic real-time data transmission is planned as final step. Here we report on our efforts to develop an acoustically positioned, ice-sensing floats featuring delayed mode data transfer (iStore).Since 1999 92 autonomous, profiling floats were deployed in the Weddell gyre area. Since 2001 these float have been registered with ARGO, forming a contribution of 61 floats in total. Since 2002, floats use the Ice Sensing Algorithm (ISA), which determines likeliness of ice coverage based on upper ocean temperatures. Of 18 ISA equipped floats 14 resurfaced after the first winter season while 11 of 13 resurfaced after the first and the second winter seasons. All of those surviving the first winter survived the second winter as well. A total of 20 floats are equipped with RAFOS receivers. Sound coverage for the RAFOS navigation system is provided by 3 sound sources installed since 2003 (2 refurbished in 2005) and 3 sources installed in 2005. Sound coverage varies according to season, location and sound source manufacturer, though a value of 400 km can be safely assumed for planning purposes

Profiling floats under sea ice in the Weddell Sea

The ARGO system is expected to form the backbone of a global ocean observing system. Its extension into the ice-covered polar oceans is difficult, since current profiling float designs have to return to the sea surface to be located and to transmit their data record. Since 1999 autonomous, profiling floats were deployed in the Weddell gyre area by the AWI-Bremerhaven, many of which failed when encountering sea-ice. This study presents results from recent float developments aimed to overcome these difficulties through ice-sensing, acoustic positioning, and intermediate data storage.Since 1999 92 autonomous, profiling floats were deployed in the Weddell gyre area. Since 2002, AWI floats feature an Ice Sensing Algorithm (ISA), which determines the likeliness of ice coverage based on upper ocean temperatures. By the end of 2004, 12 of 18 floats resurfaced after the first winter season. All of those surviving the first winter survived the second winter season as well. Thus, the overall probability of ISA equipped floats to endure the winter season is about 80% (24 of 30 instruments). A total of 20 floats are equipped with RAFOS receivers. Sound coverage for the RAFOS navigation system is provided by 3 sound sources installed since 2003 (2 refurbished in 2005) and 3 sources installed in 2005. Sound coverage varies according to season, location and sound source manufacturer, though a value of 400 km can be safely assumed for planning purposes. The intermediate data storage (iStore) technology saves profiles which could not be transmitted in real time due to ice-coverage to be transmitted at a later time. First iStored profiles are expected for February 2005