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

Abstract

The many channels of the Canadian Arctic Archipelago (CAA) represent an important export pathway for Arctic outflow waters and the transport of freshwater to the North Atlantic (Carmack et al., 2016). Located between Ellesmere Island and Greenland, Nares Strait is the northernmost outflow gateway of the Arctic Ocean, and one of two main passages through the CAA (Figure 1). Nares Strait connects the Lincoln Sea, an ice-covered continental shelf sea, with northern Baffin Bay, which harbors the ecologically significant North Water (NOW) polynya, or Pikialasorsuaq in Greenlandic (Eegeesiak et al., 2017). Nares Strait is largely a flow-through system, transporting Arctic waters southwards through a series of channels and basins, which from north to south are: Robeson Channel, Hall Basin, Kennedy Channel, Kane Basin, and finally Smith Sound (Figure 1a). The net southward volume transport through Nares Strait is estimated to be 0.8 ± 0.3 Sv, approximately equal to the net volume flux of Pacific water into the Arctic Ocean via Bering Strait (Münchow et al., 2006). In Kane Basin the

Marine diatoms record Late Holocene regime shifts in the Pikialasorsuaq ecosystem

“…An unstable Smith Sound ice arch allowed for increased export of sea ice from the Arctic Ocean into the NOW, was associated with a decline in marine primary production and little auk ( Alle alle ) colonies, and was coeval with an interval without evidence of human occupation in western Greenland (Ribeiro et al, 2021). Following Burgers et al (2023), it is possible that the positive phase of the Arctic Oscillation may have been associated with enhanced contributions of fresher and nutrient‐depleted waters from the Lincoln Sea into Nares Strait, exacerbating the unfavorable conditions for the biological productivity in the downstream NOW region. Jackson et al (2021) also inferred an increased northward inflow of Atlantic water and less efficient brine production, especially during the RWP but also during the Medieval Climate Anomaly (MCA; ca.…”

“…This current upwells in the eastern sector of the NOW to the base of the turbulent surface layer, and a flow component also veers west to feed into the south‐flowing Baffin Island Current (Dumont et al, 2010; Melling et al, 2001). Colder and fresher (<−0.4°C; <33.5 psu; Münchow et al, 2015) silicate‐ and phosphate‐rich (up to 18 and 1.1 μmol kg −1 , respectively; Burgers et al, 2023) Pacific‐derived Arctic waters have been reported to enter the NOW from the north through Nares Strait (sill depth of 220 m; Lehmann et al, 2022; Tremblay et al, 2002) driven by strong and persistent northerly winds and a sea‐level difference between the Lincoln Sea and northern Baffin Bay. However, it is worth noting that the water mass assembly and nutrient content entering Nares Strait from the Lincoln Sea vary under different atmospheric forcing patterns (i.e., Arctic Oscillation modes), with increased contribution of the fresher and nutrient‐depleted (nitrate concentrations below 1 μM during winter; Brown et al, 2020) surface waters of the Canada basin during positive phases of the Arctic Oscillation and increased contribution of the comparatively nutrient‐rich waters (nitrate concentrations up to 3.5 μmol kg −1 ) of the Siberian shelves during neutral/negative phases of the Arctic Oscillation (Burgers et al, 2023).…”

“…Colder and fresher (<−0.4°C; <33.5 psu; Münchow et al, 2015) silicate‐ and phosphate‐rich (up to 18 and 1.1 μmol kg −1 , respectively; Burgers et al, 2023) Pacific‐derived Arctic waters have been reported to enter the NOW from the north through Nares Strait (sill depth of 220 m; Lehmann et al, 2022; Tremblay et al, 2002) driven by strong and persistent northerly winds and a sea‐level difference between the Lincoln Sea and northern Baffin Bay. However, it is worth noting that the water mass assembly and nutrient content entering Nares Strait from the Lincoln Sea vary under different atmospheric forcing patterns (i.e., Arctic Oscillation modes), with increased contribution of the fresher and nutrient‐depleted (nitrate concentrations below 1 μM during winter; Brown et al, 2020) surface waters of the Canada basin during positive phases of the Arctic Oscillation and increased contribution of the comparatively nutrient‐rich waters (nitrate concentrations up to 3.5 μmol kg −1 ) of the Siberian shelves during neutral/negative phases of the Arctic Oscillation (Burgers et al, 2023). Pacific‐derived Arctic waters that are modified by meltwater input during their transit through the Canadian Arctic Archipelago also enter the NOW from the west through the shallower Lancaster (sill depth 125 m) and Jones (sill depth 190 m) sounds (Lehmann et al, 2022; Ren et al, 2022).…”

“…In this context, our results suggest that the predicted increased instability and earlier collapse of the Nares Strait ice arch for the coming decades will change the timing and taxonomic composition of seasonal phytoplankton successions and have the potential to dampen the production of small cryopelagic diatoms that are characteristic of the extended early spring bloom in the polynya. Our data further show that during the warm periods of the Late Holocene (RWP, MCA), shifts in the diatom community size structure to larger taxa that are more typical of the late(r) successional stages and subsurface conditions were associated with overall reduced export diatom production and diversity.Diatom productivity can furthermore be influenced by increased contributions of relatively nutrient-depleted water into Nares Strait during positive phases of the Arctic Oscillation(Burgers et al, 2023), as well as by feedback mechanisms such as those affecting global marine silica cycling (e.g.,Taucher et al, 2022).Therefore, there remains a risk that changes in the diatom phenology will cascade through the food web, disproportionately impacting keystone species and subsistence resources that are critically important to global biodiversity and the communities from Inuit Nunangat and Greenland.…”

Influence of Microbial Activities on Fluorescent Dissolved Organic Matter in the Dark Canada Basin Waters

“…To further elucidate the linkages between FDOM composition and microbial degradation (AOU), a water mass mixing approach was undertaken. The mixing fractions of predefined water masses using FDOM were previously estimated in the Indian Ocean (Kim et al., 2020), Nares Strait (Burgers et al., 2023), northwestern Pacific marginal seas (H. Han et al., 2023), northeast Atlantic Ocean (Álvarez‐Salgado et al., 2013), and the Arctic Ocean (Gómez‐Letona et al., 2022). Earlier studies in the Arctic Ocean have reported a positive linear relationship between humic‐like FDOM and AOU in the deep Baffin Bay/Labrador Sea waters (Gonçalve‐Araujo et al., 2016; Guéguen et al., 2014) and in the Atlantic halocline (AH) in the Canada Basin (DeFrancesco et al., 2023).…”