Arctic climate shifts drive rapid ecosystem responses across the West Greenland landscape

Prediction of high latitude response to climate change is hampered by poor understanding of the role of nonlinear changes in ecosystem forcing and response. While the effects of nonlinear climate change are often delayed or dampened by internal ecosystem dynamics, recent warming events in the Arctic have driven rapid environmental response, raising questions of how terrestrial and freshwater systems in this region may shift in response to abrupt climate change. We quantified environmental responses to recent abrupt climate change in West Greenland using long-term monitoring and paleoecological reconstructions. Using >40 years of weather data, we found that after 1994, mean June air temperatures shifted 2.2 °C higher and mean winter precipitation doubled from 21 to 40 mm; since 2006, mean July air temperatures shifted 1.1 °C higher. Nonlinear environmental responses occurred with or shortly after these abrupt climate shifts, including increasing ice sheet discharge, increasing dust, advancing plant phenology, and in lakes, earlier ice out and greater diversity of algal functional traits. Our analyses reveal rapid environmental responses to nonlinear climate shifts, underscoring the highly responsive nature of Arctic ecosystems to abrupt transitions

The Arctic in the twenty-first century: changing biogeochemical linkages across a paraglacial landscape of Greenland

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm

Assessing ecological effects of glacial meltwater on lakes fed by the Greenland Ice Sheet: The role of nutrient subsidies and turbidity

Meltwater discharge from the Greenland Ice Sheet (GrIS) exports sediment, solutes, total phosphorus (TP), dissolved inorganic nitrogen (DIN), and other macro- and micronutrients to associated aquatic ecosystems. It remains unclear how this meltwater affects the ecology of glacially fed (GF) lakes. We assessed a suite of physical, chemical, and biological features of four GF lakes, and compared them to those of four nearby snow- and groundwater-fed (SF) lakes. We found that TP concentrations were six times higher in GF compared to SF lakes, but microbial extracellular enzyme activities and aluminum, iron, and phosphorus sediment fractions suggested that much of this TP in GF lakes is likely not biologically available. Turbidity was fifteen times higher in GF lakes, and DIN was twice as high than in SF lakes, but these nitrogen differences were not significant. While diatom species richness did not significantly differ between lake types, GF lakes had higher water column chlorophyll a (Chl a). Diatom species distributions across all lakes were strongly associated with turbidity, TP, and dissolved organic carbon (DOC). While cosmopolitan diatom taxa such as Discostella stelligera were found in both lake types, diatom communities differed across lake types. For instance, Fragilaria and Psammothidium species dominated GF lakes, while Achnanthes species and Lindavia ocellata were dominant in SF lakes. In addition to turbidity, the moderate amounts of DIN in GF lakes may play an important role in shaping diatom communities. This is supported by the high abundance in GF lakes of taxa such as Fragilaria tenera and D. stelligera, which reflect nitrogen enrichment in some lakes. Our results demonstrate how GrIS meltwaters alter the ecology of Arctic lakes, and contribute to the growing body of literature that reveals spatial variability in the effects of glacial meltwaters on lake ecosystems

Earlier ice melt increases hypolimnetic oxygen despite regional warming in small Arctic lakes

Abstract Although trends toward earlier ice‐out have been documented globally, the links between ice‐out timing and lake thermal and biogeochemical structure vary spatially. In high‐latitude lakes where ice‐out occurs close to peak intensity of solar radiation, these links remain unclear. Using a long‐term dataset from 13 lakes in West Greenland, we investigated how changing ice‐out and weather conditions affect lake thermal structure and oxygen concentrations. In early ice‐out years, lakes reach higher temperatures across the water column and have deeper epilimnia. Summer hypolimnia are the warmest (~ 11°C) in years when cooler air temperatures follow early ice‐out, allowing full lake turnover. Due to the higher potential for substantive spring mixing in early ice‐out years, a warmer hypolimnion is associated with higher dissolved oxygen concentrations. By affecting variability in spring mixing, the consequences of shifts in ice phenology for lakes at high latitudes differ from expectations based on temperate regions

The Arctic in the Twenty-First Century: Changing Biogeochemical Linkages across a Paraglacial Landscape of Greenland.

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm

The Arctic in the 21st century: changing biogeochemical linkages across a paraglacial landscape of Greenland

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet, through moisture stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change due to rapid regional warming since 2000. Here we describe changes in the eco- and geomorphic systems at a range of timescales, and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and importantly, how these might change in the near future as the Arctic is expected to continue to warm