Witnessing climate change: What I have learned from my expeditions to the Greenland ice sheet

Greenland ice sheet and the Arctic region are experiencing some of the largest impacts of climate change on Earth. Since the 1990s, Greenland ice sheet surface melting has increased and is now one of the leading drivers of global sea‐level rise. For over a decade, my team and I have traveled to Greenland to study how climate change transforms the surface melting of the ice sheet. In this talk, I will share what we have learned from observing rivers on the ice sheet and tundra, and from extracting shallow ice cores high up on the ice sheet. Our ice cores show dramatically increased surface melting since the 1990s, but also a temporary melting slow‐down between 2013‐2018. In the rarely studies ice sheet surface rivers, we found surprising amounts of sediment deposited, increasing the absorption of solar radiation and melting. In this talk, I will take you on a virtual journey to one of the most remote places on earth and explore the footprints of climate change

Ogiltighetsgrunder vid olovliga värdeöverföringar - Närmare om gällande rätt vid kompetensöverskridande associerat med olovliga värdeöverföringar

Abstract The aim of this thesis is to analyse two particular situations of ineffectiveness of contract and if these can be simultaneously applicable. The first situation pertains to when the board or the CEO (Chief Executive Officer) of a corporation goes beyond its authority in performing a value transfer. The second situation pertains to unlawful value transfer as defined in Sturetvättsfallet. These two situations each have a ground of invalidity. The question arises how a court will judge according to the law if both of these situations become a legal basis. These two grounds for ineffectiveness of contract have been discussed and dealt with in Swedish case law, especially in the well known ”Sturetvättsfallet” (NJA 1999 s. 426). During this case the Swedish Supreme Court confirmed that the Swedish law regarding illegal value transfer is a priority and always applies even if the board or the CEO goes beyond the authority of the corporation. In fact this particular case ruling also dealt with the problems related to who is allowed to receive a value transfer. The case law in this field is based on the older Swedish law from 1975 and this thesis will discuss differences in the older and the current Swedish law. Keywords: Illegal value transfers 17:6. Competence violation 8:42 ABL. Sturetvättsfallet, NJA1999 s.426. Comparative study.Sammanfattning I aktiebolagslagen (2005:551) görs skillnader mellan regler, beroende på om de avser att skydda borgenärer eller aktieägare. I ett aktiebolag ansvarar ägarna inte personligen för bolagets åtaganden och förbindelser enligt 1 kap 3 § ABL. Genom kapitalskyddet som finns i 17 kap 2-3 § ABL ska bolagets borgenärer skyddas från att bolagets kapital åsidosätts. Skyddet bygger på förbud mot vissa typer av värdeöverföringar där sanktionen är bland annat ogiltighet. I 17 kap 6 § ABL beskrivs vad som utgörs av en olovlig värdeöverföring och mottagaren kan här bli återbäringsskyldig. I 17 kap 7 § ABL tas bristtäckningsansvaret upp och även skadestånd enligt 29 kap ABL kan bli aktuellt vid ogiltiga värdeöverföringar. Värdeöverföringsförbudet är utformat för att tillvarata borgenärernas och aktieägarnas skyddsintressen genom att begränsa värdeöverföringens omfattning genom olika formkrav. Då en värdeöverföring strider mot 17 kap aktiebolagslagen, oavsett överskridandet av en borgenärs- eller aktieägasskyddsregel blir rättshandlingen ogiltig. Följden blir att prestationerna ska återgå vilket gör mottagaren återbäringsskyldig. Rättshandlingar som utgör olovliga värdeöverföringar kan strida även mot behörighets- eller befogenhetsregler och tycks därför kunna aktualisera 8 kap 42 § ABL gällande kompetensöverskridande. Uppsatsen kommer i sin helhet diskutera och analysera den rättsliga ogiltigheten i fall då både ogiltighetsgrunder enligt 8 kap 42 § ABL och 17 kap 6 § ABL är parallellt tillämpliga samtidigt. Uppsatsen behandlar en stor fråga som ger upphov till fler mindre avgränsande frågor som rör värdeöverföringar enligt 17 kap ABL samt kompetensöverskridande enligt 8 kap 42 § ABL. De olika problemställningarna kommer att utgå från grundläget då ett aktiebolags ställföreträdare överskridit sin behörighet eller befogenhet genom att företa en rättshandling som strider mot 17 kap 6 § ABL om olagliga värdeöverföringar. Uppsatsen belyser även problematiska frågor som bolagets ställföreträdares kompetens och olovliga värdeöverföringars påföljder för att ge läsaren en grundläggande förståelse. Genom uppsatsens gång kommer tillbakablickar från 1975 års Aktiebolagslag bli aktuella för att läsaren ska få en fördjupad förståelse och kunskap för frågeställningarna. Ett specifikt rättsfall, NJA 1999 s.426 kommer ha stor vikt i uppsatsen för att leda läsaren genom problematiken fram till gällande rätt i frågeställningarna. Doktrin har i ämnet delade meningar om den parallella tillämpningen av ovan nämnda paragrafer och kommer att tillsammans med rättsfallen bidra till en diskussion samt förtydliga betydelsen av olika begrepp och tolkningar

A tracer study of the Arctic Ocean's liquid freshwater export variability

We present an analysis of the variability of the liquid Arctic freshwater (FW) export, using a simulation from the Community Climate System Model Version 3 (CCSM3) that includes passive tracers for FW from different sources. It is shown that the FW exported through the western Canadian Arctic Archipelago (CAA) comes mainly from the Pacific and from North American runoff. The variability of the FW export from both of these sources is generally in phase, due to the strong influence of variations of the velocity anomaly on the CAA FW export variability. The velocity anomaly in the CAA is in turn mainly governed by variations in the large-scale atmospheric circulation (i.e., the Arctic Oscillation). In Fram Strait, the FW export is mainly composed of Eurasian runoff and FW of Pacific origin. The variability of the Fram Strait FW export is governed both by changes in the velocity and in the FW concentration, and the variability of the FW concentration from the two largest sources is not in phase. The Eurasian runoff export through Fram Strait depends strongly on the release of FW from the Eurasian shelf, which occurs during years with an anticyclonic circulation anomaly (negative Vorticity index) and takes 3 years to reach Fram Strait after leaving the shelf. In contrast, the variability of the Pacific FW export through Fram Strait is mainly controlled by changes in the Pacific FW storage in the Beaufort Gyre, with an increased export during years with a cyclonic circulation anomaly (positive Vorticity index)

Greenland precipitation trends in a long-term instrumental climate context (1890-2012): evaluation of coastal and ice core records

Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series compiled from coastal meteorological stations in Greenland and Greenland Ice Sheet (GrIS) ice cores (including three new ice core records from ACT11D, Tunu2013, and Summit2010). The dataset covers the period from 1890 to 2012, a period of climate warming. For approximately the first decade of the new millennium (2001-2012) minimum and maximum mean annual precipitation conditions are found in Northeast Greenland (Tunu2013 c. 120mm water equivalent (w.e.) year-1) and South Greenland (Ikerasassuaq: c. 2300mm w.e. year-1), respectively. The coastal meteorological stations showed on average increasing trends for 1890-2012 (3.5mm w.e. year-2) and 1961-2012 (1.3mm w.e. year-2). Years with high coastal annual precipitation also had a: (1) significant high number of precipitation days (r2 = 0.59); and (2) high precipitation intensity measured as 24-h precipitation (r2 = 0.54). For the GrIS the precipitation estimated from ice cores increased on average by 0.1mm w.e. year-2 (1890-2000), showing an antiphase variability in precipitation trends between the GrIS and the coastal regions. Around 1960 a major shift occurred in the precipitation pattern towards wetter precipitation conditions for coastal Greenland, while drier conditions became more prevalent on the GrIS. Differences in precipitation trends indicate a heterogeneous spatial distribution of precipitation in Greenland. An Empirical Orthogonal Function analysis reveals a spatiotemporal cycle of precipitation that is linked instantaneously to the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation and with an �6 years lag time response to the Greenland Blocking Index. © 2014 Royal Meteorological Society

Direct Measurements of Meltwater Runoff on the Greenland Ice Sheet Surface

Meltwater runoff from the Greenland Ice Sheet surface influences surface mass balance (SMB), ice dynamics and global sea level rise, but is estimated with climate models and thus difficult to validate. We present a way to measure ice surface runoff directly, from hourly in situ supraglacial river discharge measurements and simultaneous high-resolution satellite/drone remote sensing of upstream fluvial catchment area. A first 72-hour trial for a 63.1 square kilometer moulin-terminating internally drained catchment (IDC) on Greenland's mid-elevation (1207-1381 meters above sea level) ablation zone is compared with melt and runoff simulations from HIRHAM5, MAR3.6.1 (Modele Atmospherique Regionale 3.6.1), RACMO2.3 (Regional Atmospheric Climate Model 2.3), MERRA-2 (Modern Era Retrospective-analysis for Research and Applications-2) and SEB climate/SMB models. Current models cannot reproduce peak discharges or timing of runoff entering moulins, but are improved using synthetic unit hydrograph theory (SUH). Retroactive SUH applications to two older field studies reproduces their findings, signifying that remotely sensed IDC area, shape, and river-length are useful for predicting delays in peak runoff delivery to moulins. Applying SUH to HIRHAM5, MAR3.6.1, RACMO2.3 gridded melt products for 799 surrounding IDCs suggests their terminal moulins receive lower peak discharges, less diurnal variability, and asynchronous runoff timing relative to climate/SMB model output alone. Conversely, large IDCs produce high moulin discharges, even at high elevations where melt rates are low. During this particular field experiment models overestimated runoff by plus 21 percent to plus 58 percent, linked to overestimated ablation and possible meltwater retention in bare, low-density ice. Direct measurements of ice surface runoff will improve climate/SMB models, and incorporating remotely sensed IDCs will aid coupling of surface mass balance with ice dynamics and subglacial systems

Heterogeneous CO\u3csub\u3e2\u3c/sub\u3eand CH\u3csub\u3e4\u3c/sub\u3eContent of Glacial Meltwater From the Greenland Ice Sheet and Implications for Subglacial Carbon Processes

Accelerated melting of the Greenland Ice Sheet has increased freshwater delivery to the Arctic Ocean and amplified the need to understand the impact of Greenland Ice Sheet meltwater on Arctic greenhouse gas budgets. We evaluate subglacial discharge from the Greenland Ice Sheet for carbon dioxide (CO2) and methane (CH4) concentrations and δ13C values and use geochemical models to evaluate subglacial CH4 and CO2 sources and sinks. We compare discharge from southwest (a sub-catchment of the Isunnguata Glacier, sub-Isunnguata, and the Russell Glacier) and southern Greenland (Kiattut Sermiat). Meltwater CH4 concentrations vary by orders of magnitude between sites and are saturated with respect to atmospheric concentrations at Kiattut Sermiat. In contrast, meltwaters from southwest sites are supersaturated, even though oxidation reduces CH4 concentrations by up to 50 % during periods of low discharge. CO2 concentrations range from supersaturated at sub-Isunnguata to undersaturated at Kiattut Sermiat. CO2 is consumed by mineral weathering throughout the melt season at all sites; however, differences in the magnitude of subglacial CO2 sources result in meltwaters that are either sources or sinks of atmospheric CO2. At the sub-Isunnguata site, the predominant source of CO2 is organic matter (OM) remineralization. However, multiple or heterogeneous subglacial CO2 sources maintain atmospheric CO2 concentrations at Russell but not at Kiattut Sermiat, where CO2 is undersaturated. These results highlight a previously unrecognized degree of heterogeneity in greenhouse gas dynamics under the Greenland Ice Sheet. Future work should constrain the extent and controls of heterogeneity to improve our understanding of the impact of Greenland Ice Sheet melt on Arctic greenhouse gas budgets, as well as the role of continental ice sheets in greenhouse gas variations over glacial–interglacial timescales

Greenland ice sheet surface mass loss: recent developments in observation and modeling

Surface processes currently dominate Greenland ice sheet (GrIS) mass loss. We review recent developments in the observation and modelling of GrIS surface mass balance (SMB), published after the July 2012 deadline for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). Since IPCC AR5 our understanding of GrIS SMB has further improved, but new observational and model studies have also revealed that temporal and spatial variability of many processes are still poorly quantified and understood, e.g. bio-albedo, the formation of ice lenses and their impact on lateral meltwater transport, heterogeneous vertical meltwater transport (‘piping’), the impact of atmospheric circulation changes and mixed-phase clouds on the surface energy balance and the magnitude of turbulent heat exchange over rough ice surfaces. As a result, these processes are only schematically or not at all included in models that are currently used to assess and predict future GrIS surface mass loss

Investigating the local-scale influence of sea ice on Greenland surface melt

Rapid decline in Arctic sea ice cover in the 21st century may have wide-reaching effects on the Arctic climate system, including the Greenland ice sheet mass balance. Here, we investigate whether local changes in sea ice around the Greenland ice sheet have had an impact on Greenland surface melt. Specifically, we investigate the relationship between sea ice concentration, the timing of melt onset and open-water fraction surrounding Greenland with ice sheet surface melt using a combination of remote sensing observations, and outputs from a reanalysis model and a regional climate model for the period of 1979–2015. Statistical analysis points to covariability between Greenland ice sheet surface melt and sea ice within Baffin Bay and Davis Strait. While some of this covariance can be explained by simultaneous influence of atmospheric circulation anomalies on both the sea ice cover and Greenland melt, within Baffin Bay we find a modest correlation between detrended melt onset over sea ice and the adjacent ice sheet melt onset. This correlation appears to be related to increased transfer of sensible and latent heat fluxes from the ocean to the atmosphere in early sea ice melt years, increasing temperatures and humidity over the ice sheet that in turn initiate ice sheet melt

Atmospheric drivers of Greenland surface melt revealed by self-organizing maps

Recent acceleration in surface melt on the Greenland ice sheet (GrIS) has occurred concurrently with a rapidly warming Arctic and has been connected to persistent, anomalous atmospheric circulation patterns over Greenland. To identify synoptic setups favoring enhanced GrIS surface melt and their decadal changes, we develop a summer Arctic synoptic climatology by employing self-organizing maps. These are applied to daily 500 hPa geopotential height fields obtained from the Modern Era Retrospective Analysis for Research and Applications reanalysis, 1979–2014. Particular circulation regimes are related to meteorological conditions and GrIS surface melt estimated with outputs from the Modèle Atmosphérique Régional. Our results demonstrate that the largest positive melt anomalies occur in concert with positive height anomalies near Greenland associated with wind, temperature, and humidity patterns indicative of strong meridional transport of heat and moisture. We find an increased frequency in a 500 hPa ridge over Greenland coinciding with a 63% increase in GrIS melt between the 1979–1988 and 2005–2014 periods, with 75.0% of surface melt changes attributed to thermodynamics, 17% to dynamics, and 8.0% to a combination. We also confirm that the 2007–2012 time period has the largest dynamic forcing relative of any period but also demonstrate that increased surface energy fluxes, temperature, and moisture separate from dynamic changes contributed more to melt even during this period. This implies that GrIS surface melt is likely to continue to increase in response to an ever warmer future Arctic, regardless of future atmospheric circulation patterns