Albedo-a primary control on surface melt-varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities-an admixture of dust, black carbon and pigmented algae-explain 73% of the observed spatial variability in albedo and are responsible for the dark zone itself. Crevassing and supraglacial water also drive albedo reduction but due to their limited extent, explain just 12 and 15% of the observed variability respectively. Cryoconite, concentrated in large holes or fluvial deposits, is the darkest surface type but accounts for <1% of the area and has minimal impact. We propose that the ongoing emergence and dispersal of distributed impurities, amplified by enhanced ablation and biological activity, will drive future expansion of Greenland's dark zone.
- MeSH
- ledový příkrov * MeSH
- monitorování životního prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Grónsko MeSH
Tropospheric nitrate levels are predicted to increase throughout the 21(st) century, with potential effects on terrestrial ecosystems, including the Greenland ice sheet (GrIS). This study considers the impacts of elevated nitrate concentrations on the abundance and composition of dominant bulk and active prokaryotic communities sampled from in situ nitrate fertilization plots on the GrIS surface. Nitrate concentrations were successfully elevated within sediment-filled meltwater pools, known as cryoconite holes; however, nitrate additions applied to surface ice did not persist. Estimated bulk and active cryoconite community cell abundance was unaltered by nitrate additions when compared to control holes using a quantitative PCR approach, and nitrate was found to have a minimal affect on the dominant 16S rRNA gene-based community composition. Together, these results indicate that sampled cryoconite communities were not nitrate limited at the time of sampling. Instead, temporal changes in biomass and community composition were more pronounced. As these in situ incubations were short (6 weeks), and the community composition across GrIS surface ice is highly variable, we suggest that further efforts should be considered to investigate the potential long-term impacts of increased nitrate across the GrIS.
- MeSH
- dusičnany metabolismus MeSH
- fylogeneze MeSH
- ledový příkrov mikrobiologie MeSH
- prokaryotické buňky klasifikace metabolismus MeSH
- ribozomální DNA chemie genetika MeSH
- RNA ribozomální 16S genetika MeSH
- sekvenční analýza DNA MeSH
- shluková analýza MeSH
- společenstvo účinky léků MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Grónsko MeSH
