The countdown has officially begun for our trip to Nuuk, the largest city and capital of Greenland! We’ll spend three weeks at the Greenlandic Institute of Natural Resources (GINR) and in the field collecting water samples from streams draining into the nearby fjord of Kobbefjord, which is a short boat ride from the city. Prepping for this trip feels somewhat familiar—this will be our third consecutive summer in Greenland, but our first time at the Kobbefjord site.
Kobbefjord is a unique place. Its streams have been monitored by the Asiaq Greenlandic Survey since 2006, providing a strong basis for us to study the volumes and compositions of water flowing from the landscape to the ocean. The composition of water is important for marine ecosystems because terrestrial nutrients drive phytoplankton growth. As the base of the marine food web, phytoplankton growth is important for distributions of fish and marine mammals, as well as uptake of atmospheric CO2 through photosynthesis. For our team, Kobbefjord represents another piece of the puzzle that will help us understand how the Greenlandic landscape has evolved since the retreat of the ice sheet since the Last Glacial Maximum (LGM) approximately 20,000 years ago, when ice sheets covered much of North America and Eurasia.
Our preliminary data collected over the past two summers tell us that there is more going on over the deglaciated portions of Greenland than meets the eye. We’ve been comparing small, bucolic streams of the Greenlandic tundra (nonglacial streams) to the raging proglacial torrents that drain the ever-accelerating melting of the Greenland Ice Sheet. One important discovery we’ve made is that although they are small, these small nonglacial streams contain high concentrations of nutrients (like organic carbon, nitrogen, and silica). Normalized to the area of their watersheds, our results suggest that nonglacial streams provide just as much (or even more) of these solutes to the ocean as the proglacial rivers. A key difference, however, is in the ratios of nutrients. For instance, the ratio of two of the most important nutrients for marine phytoplankton, nitrogen and phosphorus, is very different between proglacial rivers and nonglacial streams. Shifts in the delivery of these nutrients as the ice sheet retreats could significantly impact the magnitude and distribution of primary productivity in the coastal ocean. Understanding how nutrient sources and sinks work together and impact the concentrations in streams is a part of our work in Kobbefjord and will help us determine how nutrient delivery to the ocean shifts over glacial-interglacial cycles.