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1. Declining basal motion drives the long-term slowing of Athabasca Glacier, 1961-2019, Canada

   https://doi.org/10.18739/A23R0PV5K  

   Armstrong, William; Polashenski, David (January 2022, NSF Arctic Data Center)

   Globally, glaciers are shrinking in response to climate change, with implications for global sea level rise as well as downstream ecosystems and water resources. Sliding at the ice-bed interface (basal motion) provides a mechanism for glaciers to respond rapidly to climate change. While the short-term dynamics of glacier basal motion (< 10 years) have received substantial attention, little is known about how basal motion and its sensitivity to subglacial hydrology changes over long (> 50 year) timescales – this knowledge is required for accurate prediction of future glacier change. We compare historical data with modern estimates from field-collected and remotely-sensed data at Athabasca Glacier and show that, between 1961 and 2019, the glacier thinned by 51 meter ( - 18 %). However, a concurrent increase in surface slope results in minimal change in the average driving stress (-10 kilopascal, - 7%). These geometric changes coincide with a uniform surface slow down of surface velocity (-15 meter a-1, -45%). Historical observations and simplified ice modeling suggest that declining basal motion accounts for most of this slow down (63 % at a minimum). A decline in basal motion can be explained by increasing basal friction resulting from geometric change in addition to increasing meltwater flux through an efficient subglacial hydrologic system. There is some evidence that changes in basal motion in the overdeepened reach are responsible for slowing basal motion several km up-glacier. These results highlight the need to include time-varying dynamics of basal motion in glacier models and analyses. These findings suggest declining basal motion may reduce the flux of ice to lower elevations, helping to mitigate glacier mass loss in a warming climate. 

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2. 'Climate Response Functions' for the Arctic Ocean: a proposedcoordinated modeling experiment

   https://doi.org/10.5194/gmd-2016-316  

   Marshall, John; Scott, Jeffery; Proshutinsky, Andrey (July 2017, Geoscientific Model Development Discussions)

   A coordinated set of Arctic modeling experiments is proposed which explore how the Arctic responds to changes in external forcing. Our goal is to compute and compare 'Climate Response Functions' (CRFs) – the transient response of key observable indicators such as sea-ice extent, freshwater content of the Beaufort Gyre etc. – to abrupt 'step' changes in forcing fields across a number of Arctic models. Changes in wind, freshwater sources and inflows to the Arctic basin are considered. Convolutions of known or postulated time-series of these forcing fields with their respective CRFs then yields the (linear) response of these observables. This allows the project to inform, and interface directly with, Arctic observations and observers and IPCC models and the climate change community. Here we outline the rationale behind such experiments and illustrate our approach in the context of a coarse-resolution model of the Arctic based on the MITgcm. We conclude by outlining the expected benefits of such an activity and encourage other modeling groups to compute CRFs with their own models so that we might begin to document how robust they are to model formulation, resolution and parameterization. 

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3. Solar-TK: A Data-Driven Toolkit for Solar PV Performance Modeling and Forecasting

   https://doi.org/10.1109/MASS.2019.00060  

   Bashir, Noman; Chen, Dong; Irwin, David; Shenoy, Prashant (November 2019, IEEE 16th International Conference on Mobile Ad Hoc and Sensor Systems (MASS))

   Solar energy capacity is continuing to increase. The key challenge with integrating solar into buildings and the electric grid is its high power generation variability, which is a function of many factors, including a site's location, time, weather, and numerous physical attributes. There has been significant prior work on solar performance modeling and forecasting that infers a site's current and future solar generation based on these factors. Accurate solar performance models and forecasts are also a pre-requisite for conducting a wide range of building and grid energy-efficiency research. Unfortunately, much of the prior work is not accessible to researchers, either because it has not been released as open source, is time-consuming to re-implement, or requires access to proprietary data sources. To address the problem, we present Solar-TK, a data-driven toolkit for solar performance modeling and forecasting that is simple, extensible, and publicly accessible. Solar-TK's simple approach models and forecasts a site's solar output given only its location and a small amount of historical generation data. Solar-TK's extensible design includes a small collection of independent modules that connect together to implement basic modeling and forecasting, while also enabling users to implement new energy analytics. We plan to release Solar-TK as open source to enable research that requires realistic solar models and forecasts, and to serve as a baseline for comparing new solar modeling and forecasting techniques. We compare Solar-TK's simple approach with PVlib and show that it yields comparable accuracy. We present three case studies showing how Solar-TK can advance energy-efficiency research. 

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4. The first widespread solar energetic particle event of solar cycle 25 on 2020 November 29: Shock wave properties and the wide distribution of solar energetic particles

   https://doi.org/10.1051/0004-6361/202142515  

   Kouloumvakos, A.; Kwon, R. Y.; Rodríguez-García, L.; Lario, D.; Dresing, N.; Kilpua, E. K.; Vainio, R.; Török, T.; Plotnikov, I.; Rouillard, A. P.; et al (April 2022, Astronomy & Astrophysics)

   Context. On 2020 November 29, an eruptive event occurred in an active region located behind the eastern solar limb as seen from Earth. The event consisted of an M4.4 class flare, a coronal mass ejection, an extreme ultraviolet (EUV) wave, and a white-light (WL) shock wave. The eruption gave rise to the first widespread solar energetic particle (SEP) event of solar cycle 25, which was observed at four widely separated heliospheric locations (∼230°). Aims. Our aim is to better understand the source of this widespread SEP event, examine the role of the coronal shock wave in the wide distribution of SEPs, and investigate the shock wave properties at the field lines magnetically connected to the spacecraft. Methods. Using EUV and WL data, we reconstructed the global three-dimensional structure of the shock in the corona and computed its kinematics. We determined the magnetic field configurations in the corona and interplanetary space, inferred the magnetic connectivity of the spacecraft with the shock surface, and derived the evolution of the shock parameters at the connecting field lines. Results. Remote sensing observations show formation of the coronal shock wave occurring early during the eruption, and its rapid propagation to distant locations. The results of the shock wave modelling show multiple regions where a strong shock has formed and efficient particle acceleration is expected to take place. The pressure/shock wave is magnetically connected to all spacecraft locations before or during the estimated SEP release times. The release of the observed near-relativistic electrons occurs predominantly close to the time when the pressure/shock wave connects to the magnetic field lines or when the shock wave becomes supercritical, whereas the proton release is significantly delayed with respect to the time when the shock wave becomes supercritical, with the only exception being the proton release at the Parker Solar Probe. Conclusions. Our results suggest that the shock wave plays an important role in the spread of SEPs. Supercritical shock regions are connected to most of the spacecraft. The particle increase at Earth, which is barely connected to the wave, also suggests that the cross-field transport cannot be ignored. The release of energetic electrons seems to occur close to the time when the shock wave connects to, or becomes supercritical at, the field lines connecting to the spacecraft. Energetic protons are released with a time-delay relative to the time when the pressure/shock wave connects to the spacecraft locations. We attribute this delay to the time that it takes for the shock wave to accelerate protons efficiently. 

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5. The Reference Elevation Model of Antarctica

   https://doi.org/10.5194/tc-13-665-2019  

   Howat, Ian M.; Porter, Claire; Smith, Benjamin E.; Noh, Myoung-Jong; Morin, Paul (January 2019, The Cryosphere)

   Abstract. The Reference Elevation Model of Antarctica (REMA) is thefirst continental-scale digital elevation model (DEM) at a resolution ofless than 10 m. REMA is created from stereophotogrammetry with submeterresolution optical, commercial satellite imagery. The higher spatial andradiometric resolutions of this imagery enable high-quality surfaceextraction over the low-contrast ice sheet surface. The DEMs are registeredto satellite radar and laser altimetry and are mosaicked to provide acontinuous surface covering nearly 95 % the entire continent. The mosaicincludes an error estimate and a time stamp, enabling change measurement.Typical elevation errors are less than 1 m, as validated by thecomparison to airborne laser altimetry. REMA provides a powerful newresource for Antarctic science and provides a proof of concept forgenerating accurate high-resolution repeat topography at continentalscales. 

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