| Popis: |
Accelerated melting of the Greenland Ice Sheet is considered to become a tipping point in the freshwater balance of the subpolar North Atlantic (SPNA). The ramifications of increased freshwater input have been projected to reduce deep convection in neighboring Labrador and Irminger Seas. The East Greenland Current is a primary pathway for transporting Arctic-sourced freshwater and Greenland glacial meltwater into the SPNA. Understanding the variability of the East Greenland (Coastal) Current (EGC/EGCC) is of high importance, as it contains the first imprint of ice melt which flows directly into the current when entering the open ocean. We performed a cross sectional analysis of salinity and temperature along the eastern Greenland shelf using output from an eddy-rich (1/20o) ocean model (VIKING20X), which is forced with time-varying Greenland freshwater fluxes (Bamber et al., 2018), and the observational-based reanalysis product (GLORYS12V1 [1/12o]) from 1993 to 2019. A time varying mask referenced to a salinity threshold of ≤ 34.8 psu was used to isolate the EGC close to the shelf at five locations for both winter (JFM) and summer (JAS) months. Selected locations are major ocean gateways, glacier outlets/fjords, and observing arrays: Fram Strait, Denmark Strait, just south of 66oN (Helheim/~Sermilik) and 63.5oN (Bernstorff), and OSNAP East extending up to the central Irminger Sea. Export of polar water from the Arctic Ocean through Fram Strait sets the initial, low salinity signature in the EGC, which mixes with Atlantic water further downstream and increases in salinity. However, in our simulation, we find lower salinity values again south of Denmark Strait in summer with some notable fresh imprints of extreme meltwater runoff in individual years, such as 2010 and 2012. Furthermore, we observe that for all the cross sections, excluding Fram Strait, there is a negative trend in salinity from 1993 to 2010 followed by a decade in which the salinity trend at Denmark Strait and further south decouples from that in Fram Strait in winter and summer. We explore the reasons for the temporal variations in salinity (and temperature) along the East Greenland Shelf and the potential of different data products to show early imprints of enhanced meltwater runoff into the EGC. |
