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
Accounting for the climate–carbon feedback in emission metrics Earth System Dynamics DOI 10.5194/esd-8-235-2017 10 April 2017 Emission metrics such as GWP or GTP are used to put non-CO2species on aCO2-equivalentscale. In the fifth IPCC report the metrics are inconsistent, as the climate–carbon feedback is included only for CO2but not for non-CO2species. Here, we simulate a new impulse response function for the feedback, and we use it to correct the metrics. For instance, 1 g of CH4is equivalent to 31 g of CO2(instead of 28 g) following the corrected GWP100 metric. It is 34 g if other factors are also updated. Read more
Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres Atmospheric Chemistry and Physics DOI 10.5194/acp-17-4539-2017 5 April 2017 Nitrous oxide is the third most important anthropogenic greenhouse gas with an increasing mole fraction. To understand its natural and anthropogenic sources we employ isotope measurements. Results show that while the N2O mole fraction increases, its heavy isotope content decreases. The isotopic changes observed underline the dominance of agricultural emissions especially at the early part of the record, whereas in the later decades the contribution from other anthropogenic sources increases. Read more
Characterization of the long-term radiosonde temperature biases in the upper troposphere and lower stratosphere using COSMIC and Metop-A/GRAS data from 2006 to 2014 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-4493-2017 4 April 2017 Radiosonde observations (RAOBs) have provided the only long-term global in situ temperature measurements since 1958. In this study, we use Global Positioning System (GPS) radio occultation (RO) temperature data from 2006 to 2014 to characterize the inter-seasonal and interannual variability of temperature biases in the lower stratosphere. Results from this study also demonstrate the feasibility to use RO data to correct RAOB temperature biases for different sensor types. Read more
Drought and flood in the Anthropocene: feedback mechanisms in reservoir operation Earth System Dynamics DOI 10.5194/esd-8-225-2017 27 March 2017 There is still little understanding about the dynamics emerging from human–water interactions. As a result, policies and measures to reduce the impacts of floods and droughts often lead to unintended consequences. This paper proposes a research agenda to improve our understanding of human–water interactions, and presents an initial attempt to model the reciprocal effects between water management, droughts, and floods. Read more
Surge dynamics and lake outbursts of Kyagar Glacier, Karakoram The Cryosphere DOI 10.5194/tc-11-723-2017 21 March 2017 Recent surging of Kyagar Glacier (Karakoram) caused a hazardous ice-dammed lake to form and burst in 2015 and 2016. We use remotely sensed glacier surface velocities and surface elevation to observe dramatic changes in speed and mass distribution during the surge. The surge was hydrologically controlled with rapid summer onset and dramatic termination following lake outburst. Since the surge, the potential outburst hazard has remained high, and continued remote monitoring is crucial. 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
The European 2015 drought from a climatological perspective Hydrology and Earth System Sciences DOI 10.5194/hess-21-1397-2017 8 March 2017 This paper analyses the European summer drought of 2015 from a climatological perspective, including its origin and spatial and temporal development, and how it compares with the 2003 event. It discusses the main contributing factors controlling the occurrence and persistence of the event: temperature and precipitation anomalies, blocking episodes and sea surface temperatures. The results represent the outcome of a collaborative initiative of members of UNESCO’s FRIEND-Water program. Read more
Structural uncertainty in air mass factor calculation for NO2 and HCHO satellite retrievals Atmospheric Measurement Techniques DOI 10.5194/amt-10-759-2017 7 March 2017 Choices and assumptions made to represent the state of the atmosphere introduce an uncertainty of 42 % in the air mass factor calculation in trace gas satellite retrievals in polluted regions. The AMF strongly depends on the choice of a priori trace gas profile, surface albedo data set and the correction method to account for clouds and aerosols. We call for well-designed validation exercises focusing on situations when AMF structural uncertainty has the highest impact on satellite retrievals. Read more
Characteristics and causes of Deep Western Boundary Current transport variability at 34.5∘ S during 2009–2014 Ocean Science DOI 10.5194/os-13-175-2017 2 March 2017 This study investigates the variability of the Deep Western Boundary Current at 34.5° S. This current carries a large part of the cold deep limb of the Meridional Overturning Circulation, which is a crucial part of the ocean system and has impacts on global weather patterns. Study of this current in the South Atlantic has been limited in the past, and this new study provides insights into the strength and variability of the current as well as the causes for the observed changes. Read more
Soil conservation in the 21st century: why we need smart agricultural intensification SOIL DOI 10.5194/soil-3-45-2017 1 March 2017 We discuss pathways towards better soil protection in the 21st century. The efficacy of soil conservation technology is not a fundamental barrier for a more sustainable soil management. However, soil conservation is generally not directly beneficial to the farmer. We believe that the solution of this conundrum is a rapid, smart intensification of agriculture in the Global South. This will reduce the financial burden and will, at the same time, allow more effective conservation. Read more
A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera Climate of the Past DOI 10.5194/cp-13-149-2017 24 February 2017 Understanding the boron isotopic composition of seawater (δ11Bsw) is key to calculating absolute estimates of CO2 using the boron isotope pH proxy. Here we use the boron isotope gradient, along with an estimate of pH gradient, between the surface and deep ocean to show that the δ11Bsw varies by ~ 2 ‰ over the past 23 million years. This new record has implications for both δ11Bsw and CO2 records and understanding changes in the ocean isotope composition of a number of ions through time. Read more
Multi-model simulations of aerosol and ozone radiative forcing due to anthropogenic emission changes during the period 1990–2015 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-2709-2017 22 February 2017 Over the past decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990–2015, as simulated by seven global atmospheric composition models. The global mean radiative forcing is more strongly positive than reported in IPCC AR5. Read more
A new device to mount portable energy-dispersive X-ray fluorescence spectrometers (p-ED-XRF) for semi-continuous analyses of split (sediment) cores and solid samples Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-6-93-2017 17 February 2017 This paper introduces a hands-on, low-cost device (German industrial property right no. 20 2014 106 048.0) that uses common adapters to mount p-ED-XRF devices so that these can provide bulk-sedimentary chemistry data from non-destructive measurements at the surface of a split sediment core or from other solid samples. The strength of combining p-ED-XRF analyses with this new sample chamber is demonstrated by exemplary sediment cores from an archaeological research project. Read more
How much can we save? Impact of different emission scenarios on future snow cover in the Alps The Cryosphere DOI 10.5194/tc-11-517-2017 16 February 2017 We simulate the future snow cover in the Alps with the help of a snow model, which is fed by projected temperature and precipitation changes from a large set of climate models. The results demonstrate that snow below 1000 m is probably a rare guest at the end of the century. Moreover, even above 3000 m the simulations show a drastic decrease in snow depth. However, the results reveal that the projected snow cover reduction can be mitigated by 50 % if we manage to keep global warming below 2°. Read more
Brief communication: Glaciers in the Hunza catchment (Karakoram) have been nearly in balance since the 1970s The Cryosphere DOI 10.5194/tc-11-531-2017 15 February 2017 Previous geodetic estimates of glacier mass changes in the Karakoram have revealed balanced budgets or a possible slight mass gain since the year ∼ 2000. We used old US reconnaissance imagery and could show that glaciers in the Hunza River basin (Central Karakoram) experienced on average no significant mass changes also since the 1970s. Likewise the glaciers had heterogeneous behaviour with frequent surge activities during the last 40 years. Read more
Trend of atmospheric mercury concentrations at Cape Point for 1995–2004 and since 2007 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-2393-2017 15 February 2017 Currently the Cape Point GAW GEM record is a very sought-after data record for international modelers and scientist alike, as the data set of 20 years represents the longest record in the Southern Hemisphere (SH). CPT was the only monitoring site on the African continent and one of eight GMOS ground-based monitoring sites located in the SH. The increasing Hg trend observed at CPT is of global importance as treaties such as the Minamata Convention on Mercury is there to combat Hg pollution. Read more
Rapid attribution of the August 2016 flood-inducing extreme precipitation in south Louisiana to climate change Hydrology and Earth System Sciences DOI 10.5194/hess-21-897-2017 14 February 2017 During August 2016, heavy precipitation led to devastating floods in south Louisiana, USA. Here, we analyze the climatological statistics of the precipitation event, as defined by its 3-day total over 12–14 August. Using observational data and high-resolution global coupled model experiments, we find for a comparable event on the central US Gulf Coast an average return period of about 30 years and the odds being increased by at least 1.4 since 1900 due to anthropogenic climate change. Read more
Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1901-2017 9 February 2017 Modeling the interaction of dust with long-wave (LW) radiation is still a challenge due to the scarcity of information on their refractive index. In this paper, we present a unique dataset of dust refractive indices obtained from in situ measurements in a large smog chamber. Our results show that the dust LW refractive index varies strongly from source to source due to particle composition changes. We recommend taking this variability into account in climate and remote sensing applications. Read more
Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica The Cryosphere DOI 10.5194/tc-11-451-2017 8 February 2017 In this paper we investigate elevation changes of Thwaites Glacier, West Antarctica, one of the main sources of excess ice discharge into the ocean. We find that in early 2013, four subglacial lakes separated by 100 km drained suddenly, discharging more than 3 km3of water under the fastest part of the glacier in less than 6 months. Concurrent ice-speed measurements show only minor changes, suggesting that ice dynamics are not strongly sensitive to changes in water flow. Read more