Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000–2010

Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000–2010) record of summer-time energy balance components (net radiation, R n; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G) from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD) during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (β=H/LE) compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (D s) was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/R n and LE/R n and decreasing G/R n and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system

Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt. For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during summer clouds have a cooling effect over tundra and a warming effect over ice, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled with modelling efforts are essential for assessing the impact of warming in the Arctic. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13280-016-0867-5) contains supplementary material, which is available to authorized users

Climate, river discharge and suspended sediment transport in the Zackenberg River drainage basin and Young Sound/Tyrolerfjord, Northeast Greenland, 1995−2003

Climate control on river discharge, suspended sediment transport and conductivity was investigated based on high-resolution time series (1995–2003) from a High Arctic drainage basin at Zackenberg, Northeast Greenland. Data from the Zackenberg River drainage basin (512 km2) was extrapolated to estimate the total transport from land of freshwater, sediments and organic matter to the Young Sound/Tyrolerfjord system (3,016 km2). During the investigation period, a 14-day increase in thawing period, a 50-day decrease in snow cover period, an increasing release of meltwater from exposed glacier surfaces and an increasing annual runoff were recorded. The total annual runoff from the Zackenberg River drainage basin ranges between 122 and 306 million m3 (239–598 mm yr-1), while the total annual runoff to the entire Young Sound/Tyrolerfjord system ranges between 630 and 1,570 million m3 yr-1. Suspended sediment discharges from the Zackenberg River drainage basin and the entire catchment area to Young Sound/Tyrolerfjord are 15,000–130,000 t yr-1 and 77,000–670,000 t yr-1, respectively. For organic matter yield the ranges are, respectively, 1,100–11,500 t yr-1 and 6,000–59,000 t yr-1. In 2003 the total transport of carbon was 1,180 t yr-1 and 6,000 t yr-1 and of nitrate 13 t yr-1 and 66 t yr-1, respectively, for the Zackenberg River drainage basin and the entire catchment area to Young Sound/Tyrolerfjord

Comparison of treatment with insulin degludec and glargine U100 in patients with type 1 diabetes prone to nocturnal severe hypoglycaemia:The HypoDeg randomized, controlled, open-label, crossover trial

AIM: To investigate whether the long‐acting insulin analogue insulin degludec compared with insulin glargine U100 reduces the risk of nocturnal symptomatic hypoglycaemia in patients with type 1 diabetes (T1D). METHODS: Adults with T1D and at least one episode of nocturnal severe hypoglycaemia during the last 2 years were included in a 2‐year prospective, randomized, open, multicentre, crossover trial. A total of 149 patients were randomized 1:1 to basal‐bolus therapy with insulin degludec and insulin aspart or insulin glargine U100 and insulin aspart. Each treatment period lasted 1 year and consisted of 3 months of run‐in or crossover followed by 9 months of maintenance. The primary endpoint was the number of blindly adjudicated nocturnal symptomatic hypoglycaemic episodes. Secondary endpoints included the occurrence of severe hypoglycaemia. We analysed all endpoints by intention‐to‐treat. RESULTS: Treatment with insulin degludec resulted in a 28% (95% CI: 9%‐43%; P = .02) relative rate reduction (RRR) of nocturnal symptomatic hypoglycaemia at level 1 (≤3.9 mmol/L), a 37% (95% CI: 16%‐53%; P = .002) RRR at level 2 (≤3.0 mmol/L), and a 35% (95% CI: 1%‐58%; P = .04) RRR in all‐day severe hypoglycaemia compared with insulin glargine U100. CONCLUSIONS: Patients with T1D prone to nocturnal severe hypoglycaemia have lower rates of nocturnal symptomatic hypoglycaemia and all‐day severe hypoglycaemia with insulin degludec compared with insulin glargine U100