Moored observations of synoptic and seasonal variability in the East Greenland Coastal Current

Abstract

We present a year-round assessment of the hydrographic variability within the East Greenland Coastal Current on the Greenland shelf from five synoptic crossings and 4 years of moored hydrographic data. From the five synoptic sections the current is observed as a robust, surface intensified flow with a total volume transport of 0.66 6 0.18 Sv and a freshwater transport of 42 6 12 mSv. The moorings showed heretofore unobserved variability in the abundance of Polar and Atlantic water masses in the current on synoptic scales. This is exhibited as large vertical displacement of isotherms (often greater than 100 m). Seasonally, the current is hemmed into the coast during the fall by a full depth Atlantic Water layer that has penetrated onto the inner shelf. The Polar Water layer in the current then thickens through the winter and spring seasons increasing the freshwater content in the current; the timing implies that this is probably driven by the seasonally varying export of freshwater from the Arctic and not the local runoff from Greenland. The measured synoptic variability is enhanced during the winter and spring period due to a lower halocline and a concurrent enhancement in the along-coast wind speed. The local winds force much of the high-frequency variability in a manner consistent with downwelling, but variability distinct from downwelling is also visible.

Heat, Salt, and Freshwater Budgets for a Glacial Fjord in Greenland

“…The water masses found in the fjord are a combination of shelf water masses-Atlantic Water (AW) and Polar Water (PW)-and glacially modified water from submarine meltwater and runoff (Straneo et al 2011). Because there are at least four different water mass end-members, the meltwater fraction cannot be unambiguously calculated with measurements of temperature and salinity alone (Beaird et al 2015).…”

“…The southeast shelf of Greenland is subjected to intense alongshore winds, called barrier winds, which occur when low-pressure systems encounter Greenland's steep topography (Harden et al 2011). Outside of Sermilik, these strong winds are typically from the northeast, which is downwellingfavorable from an oceanographic perspective.…”

Dynamics of Greenland�s glacial fjords

“…Outside of Sermilik, these strong winds are typically from the northeast, which is downwelling-favorable from an oceanographic perspective. The shelf region is characterized by strong oceanic fronts and large variability in water properties, with a series of troughs diverting the East Greenland Coastal Current in close proximity to Sermilik's mouth (Sutherland and Pickart, 2008;Harden et al, 2014). Sermilik…”

“…These pulses originate on the shelf and are driven by fluctuations in the shelf pycnocline. Shelf density fluctuations, in turn, are primarily associated with along-shore shelf winds (Jackson et al, 2014;Harden et al, 2014). The shelf-forced flows drive large volume fluxes into and out of the fjord, causing significant variability in heat content and salinity -due both to heaving of isopycnals and also to advective property changes within isopycnal layers (Jackson et al, 2014).…”

“…On synoptic timescales of 2 to 10 day periods (subinertial and subtidal), the fjord flows are highly coherent with upstream shelf density and also (to a lesser extent) shelf wind. Shelf density fluctuations are primarily driven by regional along-shore winds, but other sources of variability exist (Harden et al, 2014). These two fjords on the southeast coast of Greenland are in a region of exceptionally strong winds.…”