Seabird populations serve as sensitive indicators of marine ecosystem health and climate change impacts. This study synthesizes three decades (1995-2025) of seabird monitoring data from Iceland and the Faroe Islands, integrating breeding colony censuses, diet analysis, tracking studies, and oceanographic data. We assessed population trends for 15 species representing different foraging guilds and ecological niches. Results reveal divergent trajectories: surface-feeding species (Arctic tern, black-legged kittiwake) declined by 40-65%, while diving species showed mixed trends with Atlantic puffin populations stabilizing after earlier declines. Diet analysis showed reduced sand eel availability, with breeding success strongly correlated with sand eel abundance indices (r2 = 0.72 for puffins). GPS tracking revealed altered foraging ranges, with birds traveling 35% farther on average compared to 2000-2005 baseline periods. Oceanographic analysis links prey declines to increased sea surface temperatures affecting sand eel recruitment and distribution shifts of other forage fish. Climate envelope models project continued range contractions for cold-water adapted species. These findings inform marine protected area design and highlight seabirds' utility as ecosystem indicators.

Iceland's geothermal hot springs harbor unique microbial communities adapted to extreme conditions, offering insights into early Earth environments and the limits of life. This study employed metagenomic sequencing and geochemical analysis to characterize microbial diversity and metabolic potential across 24 hot springs spanning temperatures of 45-98 degrees C and pH values of 2.5-9.2. We recovered 892 metagenome-assembled genomes (MAGs), including 156 representing novel species and 12 potentially novel genera. Community composition was primarily structured by temperature and pH, with distinct assemblages in acidic sulfur-rich springs versus alkaline silica-depositing systems. Thermophilic Crenarchaeota dominated above 80 degrees C, while bacterial diversity peaked at 60-70 degrees C. Metabolic reconstruction revealed widespread capacity for sulfur and hydrogen oxidation, with novel pathways for arsenic resistance and heavy metal detoxification. Carbon fixation occurred primarily through the reverse TCA cycle and the 3-hydroxypropionate/4-hydroxybutyrate pathway. We identified syntrophic relationships between hydrogen-producing fermenters and hydrogenotrophic methanogens in moderate-temperature springs. These findings expand understanding of thermophilic microbial ecology and reveal biotechnologically relevant enzymes for industrial applications.

High-resolution paleoclimate records from the North Atlantic region are essential for understanding natural climate variability and contextualizing recent warming. We present a multi-proxy paleoclimate reconstruction spanning the past 12,000 years from Hvitarvatn, a glacier-fed lake in central Iceland. Analysis of sediment cores included varve counting, tephra identification, biogenic silica, total organic carbon, carbon/nitrogen ratios, and compound-specific hydrogen isotopes from leaf waxes. The record reveals substantial Holocene temperature variability, with the Holocene Thermal Maximum (8,000-5,000 years BP) featuring summer temperatures 2-3 degrees C warmer than the 20th-century average. Neoglacial cooling commenced around 5,000 years BP, culminating in the Little Ice Age (1300-1900 CE). Glacier extent reconstructed from varve thickness indicates multiple advances and retreats, with at least six periods of expansion comparable to or exceeding Little Ice Age conditions. Notably, the past 100 years show summer warming exceeding any centennial-scale event in the Holocene record. Spectral analysis identifies significant periodicities at 200, 500, and 1,000 years, suggesting solar and ocean circulation forcing. These findings provide crucial baseline data for evaluating anthropogenic climate change in the North Atlantic.

Sustainable geothermal energy extraction requires detailed understanding of reservoir dynamics and fluid recharge processes. This study presents 15 years of comprehensive monitoring data from the Hellisheidi geothermal power station, one of the world's largest geothermal facilities producing 303 MW of electricity. We analyzed pressure evolution in 65 production and monitoring wells, tracer test results, fluid geochemistry time series, and micro-seismic activity. Results reveal a complex pattern of pressure drawdown, with the main production zone declining by 15 bar since 2006 while reinjection zones show localized pressure recovery. Tracer tests indicate primary fluid travel times of 2-8 years from reinjection wells to production zones, suggesting substantial residence times for thermal recovery. Geochemical monitoring shows progressive mixing between deep reservoir fluids and shallower groundwater, with silica concentrations declining by 8% indicating cooling of production zones. Induced seismicity remained below M2.5 throughout the monitoring period. We present a numerical reservoir model validated against monitoring data and use it to evaluate long-term production scenarios, recommending optimized reinjection strategies to maintain pressure support.

The waters surrounding Iceland represent a critical transition zone between North Atlantic and Arctic marine ecosystems, making them highly sensitive to climate-driven changes. This study examines shifts in marine primary productivity and trophic dynamics over 2000-2025 using satellite ocean color data, continuous plankton recorder surveys, and fish stock assessments. Sea surface temperatures increased by 1.3 degrees C on average, with pronounced warming (2.1 degrees C) north of Iceland. Phytoplankton bloom timing advanced by 18 days, and the species composition shifted toward smaller, warm-water affiliated taxa. Annual primary production increased by 12% overall but with significant spatial heterogeneity. Zooplankton community structure changed markedly, with the subarctic copepod Calanus finmarchicus declining by 30% while the smaller C. helgolandicus expanded northward. These plankton shifts propagated through the food web, affecting recruitment success of commercially important fish species including cod and capelin. Our findings demonstrate cascading ecosystem effects of ocean warming and highlight the need for adaptive fisheries management strategies.

Climate warming is causing widespread permafrost degradation in subarctic mountain regions, with significant implications for slope stability and natural hazards. This comparative study examines permafrost-related mass movements in Iceland's central highlands and northern Scandinavia's mountain belt. Using a combination of ground temperature monitoring (85 boreholes), electrical resistivity tomography, InSAR-derived surface deformation data, and historical landslide inventories, we assessed the relationship between permafrost warming and slope failure frequency. Results show mean annual ground temperatures have increased by 0.6-1.2 degrees C since 2000, with active layer thickness expanding by 15-40 cm. The frequency of debris flows and rockfalls has increased by 180% in permafrost-affected terrain compared to pre-2000 baselines. We identified critical thermal thresholds at -0.5 degrees C mean annual ground temperature where slope failure probability increases exponentially. A susceptibility model incorporating permafrost thermal state, slope angle, and lithology achieved 85% accuracy in predicting recent failures. These findings inform infrastructure planning and hazard management in permafrost-sensitive regions.

The November 2024 eruption of Grimsvotn volcano beneath Vatnajokull ice cap triggered one of the largest jokulhlaups (glacial outburst floods) recorded in the past century. This paper presents a detailed reconstruction of the eruptive sequence, ice-volcano interactions, and subsequent flooding using seismic networks, GPS measurements, satellite imagery, and hydrological monitoring. The eruption produced approximately 0.8 km3 of tephra and melted an estimated 3.2 km3 of ice within 72 hours. The resulting jokulhlaup reached a peak discharge of 45,000 m3/s at Gigjukvisl, causing significant damage to infrastructure on the Skeidararsandur outwash plain. Our analysis identifies precursor signals detectable 48-72 hours before eruption onset, including subtle ice cauldron subsidence, increased seismicity, and GPS-detected inflation. We propose an integrated early warning system combining these parameters to improve evacuation lead times. The event demonstrates the ongoing hazard posed by Iceland's ice-covered volcanoes in a warming climate where reduced ice thickness may alter eruption dynamics.

This study presents a comprehensive analysis of glacier mass changes in the Vatnajokull ice cap, Iceland's largest glacier, over the period 1995-2025. Integrating CryoSat-2 and ICESat-2 satellite altimetry data with ground-based stake measurements from 45 monitoring sites, we quantified spatiotemporal patterns of mass loss with unprecedented precision. Results indicate an acceleration in mass loss from -0.8 m w.e. yr-¹ during 1995-2010 to -1.4 m w.e. yr-¹ during 2015-2025, representing a 75% increase in ablation rates. The most pronounced thinning occurred in outlet glaciers terminating in proglacial lakes, where calving dynamics amplified mass loss. Our analysis reveals that summer temperature increases of 1.8 degrees C since 1995 account for 65% of the observed acceleration, while reduced winter precipitation contributed 25%. Projections using regional climate models suggest Vatnajokull could lose 25-40% of its current volume by 2100 under moderate emission scenarios. These findings have significant implications for sea level rise projections, hydropower generation, and Icelandic freshwater resources.