Atlantic-Origin Overflow Water in the East Greenland Current

Abstract

Dense water masses transported southward along the east coast of Greenland in the East Greenland Current (EGC) form the largest contribution to the Denmark Strait Overflow. When exiting Denmark Strait these dense water masses sink to depth and feed the deep circulation in the North Atlantic. Based on one year of mooring observations upstream of Denmark Strait and historical hydrographic profiles between Fram Strait and Denmark Strait, we find that a large part (75%) of the overflow water (σθ ≥ 27.8 kg m−3) transported by the EGC is of Atlantic origin (potential temperature θ > 0°C). The along-stream changes in temperature of the Atlantic-origin Water are moderate north of 69°N at the northern end of Blosseville basin, but southward from this point the temperature decreases more rapidly. We hypothesize that this enhanced modification is related to the bifurcation of the EGC taking place close to 69°N into the shelfbreak EGC and the separated EGC. This is associated with enhanced eddy activity and strong water mass modification reducing the intermediate temperature and salinity maxima of the Atlantic-origin Water. During periods with a large (small) degree of modification the separated current is strong (weak). Output from a high-resolution numerical model supports our hypothesis and reveals that large eddy activity is associated with an offshore shift of the surface freshwater layer that characterizes the Greenland shelf. The intensity of the eddy activity regulates the density and the hydrographic properties of the Denmark Strait Overflow Water transported by the EGC system.

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

“…Therefore, we use the 15‐km resolution Arctic System Reanalysis (ASRv2; Bromwich et al, ), which represents a significant improvement (Bromwich et al, ) in horizontal resolution of the atmospheric forcing previously implemented (ERA‐Interim; Dee et al, ). The model solutions have been also compared to data collected upstream of Denmark Strait by Håvik et al (). Vertical sections of hydrographic and velocity fields are consistent with the validation performed by Almansi et al ().…”

Wintertime Water Mass Transformation in the Western Iceland and Greenland Seas

“…Farther south, more PSW was found offshore of the slope in the western Iceland Sea (with no significant change in the layer thickness). This regional difference in PSW presence is not surprising considering the enhanced instability of EGC in the Iceland Sea, which leads to a greater flux of properties from the slope to the interior (Håvik et al., 2019; Våge et al., 2013). Previous studies suggested that the distribution of PSW plays an important role in influencing the formation of deep mixed layers in the western Iceland and Greenland Seas (Våge et al., 2018).…”

Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges

“…Therefore, we use the 15-km resolution Arctic System Reanalysis (ASRv2; Bromwich et al, 2018), which represents a significant improvement (Bromwich et al, 2016) in horizontal resolution of the atmospheric forcing previously implemented (ERA-Interim; Dee et al, 2011). The model solutions have been also compared to data collected upstream of Denmark Strait by Håvik et al (2019). Vertical sections of hydrographic and velocity fields are consistent with the validation performed by Almansi et al (2017).…”