Multidecadal Water Mass Dynamics on the West Greenland Shelf

Abstract

The waters on the West Greenland continental shelf and slope play an important role in the global climate system with their link to the subpolar North Atlantic Ocean circulation system and the Greenland Ice Sheet. Lately, low temperature waters on the West Greenland shelf have been observed as far south as ∼64°N and associated with a cold and relatively saline water mass originating north of Davis Strait in Baffin Bay referred to as Baffin Bay Polar Water (BBPW). Here we use long, seasonal hydrographic time series from West Greenland at ∼64°N to study how frequently BBPW is reaching this far south. The analysis covers the period 1950–2018 with a data gap between 1988 and 2005. BBPW was observed frequently and was responsible for the temperature changes observed in the late 1960s–1980s and more intermittently post‐2008. Some of the large temperature changes we observe in the time series have previously been ascribed to “Great Salinity Anomalies” (GSAs) propagating around the subpolar North Atlantic Ocean circulation system. The prevailing view of the propagation of GSAs has been ascribed to advection of anomalies along the large‐scale circulation system. Our study shows that BBPW may play an important role in the interpretation of GSAs and melt of the Greenland Ice Sheet. Large temporal temperature changes at ∼64°N are associated with arrival of BBPW from the north and not advection of anomalies with the large‐scale current system from the south. This advocates for a shift in water masses caused by changes in the position and/or strength of oceanic currents.

Influence of glacier type on bloom phenology in two Southwest Greenland fjords

“…In brief, there is an upper layer of relatively cool and fresh southwest Greenland coastal water (CW), and a lower layer of warmer and more saline subpolar mode water (SPMW), further distinguished by an upper layer (uSPMW) and a cooler and less saline deep layer (dSPMW). Occasionally the upper layer of the coastal waters at 64 • N is occupied by a cold and relatively saline Baffin Bay Polar Water (BBPW), a winter mode water mass originating in the eastern part of Baffin Bay (Mortensen et al, 2022). Seasonal hydrography and circulation modes have been described extensively for Nuup Kangerlua (Mortensen et al, 2011(Mortensen et al, , 2013(Mortensen et al, , 2014 and for Ameralik in the same year as this study (Stuart-Lee et al, 2021).…”

Distinguishing Physical and Biological Controls on the Carbon Dynamics in a High‐Arctic Outlet Strait

“…Much remains unknown about water mass transport from the WGC and variability in the NOW region (Mortensen et al., 2022). However, a number of recent modeling studies align in predicting that the strength of the WGC, and the amount of heat it transports around Baffin Bay in the SPMW layer, will likely increase in the future (Buchart et al., 2022; Castro de la Guardia et al., 2015; Gillard et al., 2020; Grivault et al., 2017).…”

“…Across the North Water polynya region of northern Baffin Bay we observe another two water masses entering Nares Strait from the southeast. The upper water column is dominated by Baffin Bay Polar water (BBPW), a winter mode water formed somewhere in eastern Baffin Bay (Mortensen et al., 2022; Rysgaard et al., 2020), characterized by a near‐surface temperature minimum close to the freezing point and a salinity of approximately 33.5. Centered at 300 m depth we also observe a relatively warm ( T = 2°C) and saline ( S = 34.3) Subpolar Mode Water (SPMW) layer transiting northwards.…”

“…Water masses in each source region were identified by their unique physicochemical characteristics (e.g., temperature minimum, nutrient maximum). We identified three water masses arriving from the northern source region: Polar Mode water (PMW), Upper Halocline water (UHW), and Canada Basin Atlantic water (CBAW); and another two source water masses arriving from the southern source region: Baffin Bay Polar water (BBPW) and Subpolar Mode water (SPMW) (Mortensen et al., 2022; Rysgaard et al., 2020). The specific properties and origins of each source water mass is described in Section 3.1.…”

“…The NOW polynya region in northern Baffin Bay has its own unique water column characteristics, governed by the convergence of Arctic outflow waters from Nares Strait with a separate water mass assembly transported northwards by the West Greenland Current (WGC) from the subpolar North Atlantic (Bâcle et al., 2002; Lobb et al., 2003; Melling et al., 2001; Mortensen et al., 2022; Rysgaard et al., 2020). At the front where these two water mass assemblies meet, cross‐frontal gradients in temperature and salinity have been found to be largely density compensating, leading to a high degree of isopycnal interleaving (Lobb et al., 2003).…”