Environmental Analysis and Remote Sensing (Netherlands)

<strong class="journal-contentHeaderColor">Abstract.</strong> Ice-core reconstructions indicate that increased snow accumulation on the Antarctic Ice Sheet mitigated global sea level rise by ~11 mm during 1901&ndash;2000. However, in the most recent 40 years of more intense observation and warming, the trend in the Antarctic-wide accumulation rate has been negligible. We attribute these trends by evaluating Earth system model experiments in comparison with dynamically consistent reconstructions of surface climate. Single-forcing experiments reveal that rising concentrations of greenhouse gases (GHGs) have been the underlying driver of increased accumulation, yet acting alone would have caused twice the observed accumulation-related sea level mitigation during 1901&ndash;2000. Aerosol-driven cooling partially compensates this overprediction, but there is strong evidence for other processes at work. We hypothesize that high-latitude winds have been working together with ice-shelf meltwater fluxes to dampen Southern Ocean surface warming and suppress the GHG-driven accumulation increase since the initiation of West Antarctic ice shelf thinning in the mid-twentieth century. The wind pattern associated with strengthening of the Southern Hemisphere westerlies and deepening of the Amundsen Sea Low distributes accumulation unevenly across the continent in an orographic pattern that is consistent across models and the reconstructions. In reconstructions, these same wind and accumulation patterns are associated with muted surface warming across the eastern Pacific and Southern Ocean, a pattern not captured in climate projections including the all-forcings large ensemble studied here. However, the westerly wind history constrained by paleoclimate data assimilation largely reconciles differences between the model's ensemble-mean response and the observed world for both Antarctic-wide accumulation and large-scale warming patterns. Although the large ensemble simulates similar wind histories to the real one, its corresponding responses in SSTs and Antarctic-wide accumulation are decoupled from the wind. We discuss how this significant observation-model discrepancy, which has widespread implications for projecting regional climate change, likely arises from omitted meltwater forcing and/or resolution limitations. As a component of the sea level budget and a gauge of the magnitude and spatial pattern of climate change, Antarctic snow accumulation is a critical target for models to replicate.

Accurate measurements of snowfall in mid- and high-latitudes are particularly important, because snow provides a vital freshwater source, and impacts glacier mass balances as well as surface albedo. However, ice water content (IWC) and snowfall rates (SR) are hard to measure due to their high spatial variability and the remoteness of polar regions.Here, we present novel ice water content - equivalent radar reflectivity (IWC-Ze) and snowfall rate - equivalent radar reflectivity (SR-Ze) relations for 40&amp;#176; slanted and vertically pointing W-band cloud radar. The relations are derived from joint in situ snowfall and remote sensing (radar and radiometer) data from the SAIL site (Colorado, USA) and validated for sites in Hyyti&amp;#228;l&amp;#228; (Finland), Ny-&amp;#197;lesund (Svalbard, Norway), and Eriswil (Switzerland). In addition, gauge measurements from SAIL and Hyyti&amp;#228;l&amp;#228; are used as an independent reference for validation. We show the dependence of IWC-Ze and SR-Ze on riming, which we utilize to reduce the spread in the IWC-Ze and SR-Ze spaces. Normalized root mean square errors (NRMSE) are below 25% for IWC&gt;0.1 gm&amp;#8315;&amp;#179;. For SR, the NRMSE is below 70% over the whole SR range. We also present relations using liquid water path (LWP) as a proxy for the occurrence of riming, which can be applied to both ground-based and space-borne radar-radiometer instruments. The latter is demonstrated using the example of the proposed ESA Earth Explorer 11 candidate mission WIVERN, which consists of a conical scanning 94 GHz radar and a passive 94 GHz radiometer. With this approach, NRMSE are below 75% for IWC&gt;0.1 gm&amp;#8315;&amp;#179; and below 80% for SR&gt;0.2 mmhr&amp;#8315;&amp;#185;.The proposed IWC and SR relations provide a novel way to reduce uncertainties of IWC and SR estimates for W-band radar by accounting for particle riming. Advantages to current literature relations are the flexibility in terms of viewing angle and the inclusion of LWP, allowing the application to ground-based and space-borne radar-radiometer combinations like EarthCARE or the proposed WIVERN mission.

The ESA Earth System Model (ESA ESM; Dobslaw et al., 2015) is widely applied as a source model in end-to-end simulation studies for future gravity missions but has been also utilised to study novel gravity observing concepts on the ground. The model provides a synthetic time-variable global gravity field that includes realistic mass variations in the atmosphere, oceans, terrestrial water storage, continental ice sheets and the solid Earth for a variety of spatial and temporal frequencies. With the continuous development of the next gravity missions such as GRACE-C and NGGM / MAGIC, the ESM should provide a wide range of signals at spatial scales which might not have been reliably observed by currently active missions.In this contribution, we present the first steps towards version 3.0 of the ESA ESM. The projected changes include an update of the atmosphere and ocean components, a small ensemble of co- and post-seismic earthquake signals, an updated GIA model, and additional mass balance signals from previously not considered Arctic glaciers. Extreme hydrometeorological events as well as climate-driven and anthropogenic impacts on continental water storage will be represented through an update of the hydrological component. Additionally, the ESM will separately include ocean bottom pressure variations along the western slope of the Atlantic, representing variations in the meridional overturning circulation. ESA ESM 3.0 will be available with 6 hourly resolution from January 2007 until December 2020. It will be also augmented with synthetic error time-series to facilitate stochastical modelling of residual background model errors.Dobslaw, H., Bergmann-Wolf, I., Dill, R., Forootan, E., Klemann, V., Kusche, J., &amp;amp; Sasgen, I. (2015). The updated ESA Earth System Model for future gravity mission simulation studies. Journal of Geodesy, 89(5), 505&amp;#8211;513. https://doi.org/10.1007/s00190-014-0787-8

Abstract Modeling the short‐term (&lt;50 years) evolution of glaciers is difficult because of issues related to model initialization and data assimilation. However, this timescale is critical, particularly for water resources, natural hazards, and ecology. Using a unique record of satellite remote‐sensing data, combined with a novel optimisation and surface‐forcing‐calculation method within the framework of the deep‐learning‐based Instructed Glacier Model, we are able to ameliorate initialization issues. We thus model the committed evolution of all glaciers in the European Alps up to 2050 using present‐day climate conditions, assuming no future climate change. We find that the resulting committed ice loss exceeds a third of the present‐day ice volume by 2050, with multi‐kilometer frontal retreats for even the largest glaciers. Our results show the importance of modeling ice dynamics to accurately retrieve the ice‐thickness distribution and to predict future mass changes. Thanks to high‐performance GPU processing, we also demonstrate our method's global potential.

Abstract Natural gas is considered a bridging technology in the energy transition because it produces fewer carbon emissions than coal, for example. However, when leaks exist, methane is released into the atmosphere, leading to a dramatic increase in the carbon footprint of natural gas, as methane is a much stronger greenhouse gas than carbon dioxide. Therefore, we conducted a detailed study of methane emissions from gas‐powered end‐use appliances and then compared their climate impacts with those of electricity‐powered appliances. We used the Munich Oktoberfest as a case study and then extended the study to 25 major natural gas consuming countries. This showed that electricity has been the more climate‐friendly energy source at Oktoberfest since 2005, due to the extensive use of renewable electricity at the festival and the presence of methane emissions, particularly caused by the incomplete combustion and leakages of natural gas in cooking and heating appliances. By contrast, at the global level, our study shows that natural gas still produces lower carbon emissions for end‐user appliances than electricity in 18 of the 25 countries studied. However, as the share of renewable energy in the electricity mix steadily increases in most countries, the carbon footprint of electricity will be lower than that of natural gas in these countries in the near future. These findings from our comparison of the total carbon emissions of electric and gas‐powered end‐use appliances can help inform the debate on how to effectively address climate change.

Spatial modelling of hydrological and erosion processes at watershed scale is subject to an increasing development simultaneously with the expanded use of remote sensing and geographical information systems (GIS). Nevertheless, the raster structure of available spatial erosion models does not take into account some human landscape dimensions. Linear and directional features are commonly neglected in water and sediment transport modelling. This paper presents an attempt for integrating influences of spatial pattern discontinuities and directivity effects due to tillage and row of plants on the distribution of flows in agricultural watersheds. Introduction of these improvements in the ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) model are in process.

Abstract This paper reports the application of deriving evapotranspiration and thermal inertia from thermal and visible infrared Meteosat data to Sahelian wetlands: the Niger Delta in Mali and the Logone/Chari/Chad system in Chad.