1 Introduction

Baffin Bay is a semienclosed water body bounded by Greenland on the east, Baffin Island on the west, the Canadian Arctic Archipelago (CAA) to the north, and Davis Strait to the south (Figure 1a). Within the basin, the circulation is cyclonic, and the waters are a mix of relatively warm and saline Atlantic water, cold and low‐salinity Arctic water, and meltwater from the Greenland ice sheet.

Figure 1 Open in figure viewer PowerPoint Study area and experiment setup. (a) A generalized representation of the general circulation within Baffin Bay and water exchanges. Circulation through the Canadian Arctic Archipelago (CAA, group of islands to the west of Baffin Bay) regulates the exchanges between Arctic Ocean and Baffin Bay. Cold Arctic waters enter Baffin Bay through Lancaster Sound (LS), Jones Sound (JS), and Nares Strait (NS) (black boxes). Arctic water exiting through Fram Strait (FS) also enters Baffin Bay through Davis Strait (DS) in the upper 200 m of the West Greenland Current (WGC). Warm Atlantic water enters Baffin Bay through DS at depth (below 200 m) in the WGC (red dash line). (b) Experiments are set up with runoff added on the northwest Greenland coast (blue‐shaded area). Experiment runoff788b includes, in addition to runoff in the northwest, runoff along the southwest and southeast coasts (green‐shaded area). Calculations of temperature and heat content of the west Greenland shelf (WGS) are done by integrating the temperature and heat changes within the gray‐shaded region. A list of the experiments is presented with details about the setup.

The Atlantic‐origin waters enter Baffin Bay at depths of 200–600 m in the northward flowing west Greenland slope current through eastern Davis Strait [Tang et al., 2004; Curry et al., 2011; Azetsu‐Scott et al., 2012; Curry et al., 2014]. Within Baffin Bay, this inflow forms a warm subsurface layer that is hereafter referred to as the west Greenland Irminger water (WGIW).

Near the surface (depths ranging 30–200 m), flowing over the west Greenland shelf and slope, is the West Greenland Current (WGC) carrying modified Arctic water that exited the Arctic Ocean through Fram Strait [Tang et al., 2004; Myers and Ribergaard, 2013; Curry et al., 2014]. However, the main source of Arctic water into Baffin Bay is through the three channels of the CAA: Nares Strait, Jones Sound, and Lancaster Sound [Tang et al., 2004; Curry et al., 2014]. The Arctic water entering through the CAA is colder than Arctic water in the WGC [Gladish et al., 2015].

The meltwater signal from the Greenland ice sheet is found in the upper 30 m of the water column. It enters Baffin Bay as glacier melt and icebergs that break off the tongue of marine‐terminating glaciers [Tang et al., 2004]. Typically, glaciers in Greenland end in fjords which can be more than 800 m deep but have sill depths ranging from 150 to 250 m at the mouth of the fjord [Johannessen et al., 2011; Myers and Ribergaard, 2013; Gladish et al., 2015]. The circulation within a fjord is driven by the basal melting and subglacial discharge, and it is separated from the larger‐scale circulation of Baffin Bay by the sill [Rignot et al., 2010; Straneo et al., 2010; Johannessen et al., 2011; Straneo and Heimbach, 2013; Gladish et al., 2015].

This in‐fjord circulation constitutes a major difference between Greenland and Antarctica in regard to how the meltwater from the glaciers interact with the nearby ocean circulation. In Antarctica, the ice shelves, which drain 80% of the ice sheet, are in contact with the large‐scale ocean circulation [Pritchard et al., 2012]; thus, mixing due to glaciers melting at depth could have an impact on the ocean at large. In Greenland, however, mixing and entrainment due to glaciers melting at depths happen within the fjords [Rignot et al., 2010; Straneo et al., 2010; Johannessen et al., 2011; Straneo and Heimbach, 2013; Gladish et al., 2015].

In Greenland, the low‐salinity water from glaciers melting at depth rises within the fjord and then flows out of the fjord as a surface current [Rignot and Steffen, 2008; Rignot et al., 2010; Motyka et al., 2011; Straneo and Heimbach, 2013]. This drives a return flow at depth, which in Baffin Bay is near the depth range of the WGIW [Holland et al., 2008; Loyd et al., 2011; Myers and Ribergaard, 2013]. The sill at the mouth of the fjords is the only obstacle to warm shelf waters entering a fjord and contributing to the melting of tidewater glaciers [Holland et al., 2008; Rignot et al., 2010; Straneo et al., 2010; Johannessen et al., 2011; Straneo and Heimbach, 2013; Myers and Ribergaard, 2013; Gladish et al., 2015]. In this framework, marine‐terminating glaciers in northwest Greenland are exposed to rising Atlantic Ocean temperatures and the associated changes in the WGIW heat content [Rignot and Steffen, 2008; Rignot et al., 2010; Myers and Ribergaard, 2013].

In recent decades and coincident with warmer subsurface waters entering the fjords, there has been an acceleration in the melting rate of northwest Greenland glaciers [Holland et al., 2008; Motyka et al., 2011; Straneo and Heimbach, 2013; Myers and Ribergaard, 2013]. In anticipation of further melt from the Greenland ice sheet [Church et al., 2013], further study of how Baffin Bay shelf waters may respond to enhanced meltwater production is warranted. Previous studies showed that increased meltwater discharge from Greenland reduces the CAA throughflow and freshens the surface waters in Baffin Bay within 5 years [Rudels, 2011; Brunnabend et al., 2012]. The Arctic inflow through the CAA is a large source of cold water; thus, it has an important cooling effect on Baffin Bay. The freshening of surface waters stabilizes the near‐surface water column, which reduces vertical mixing and heat loss by the warmer subsurface water [Brunnabend et al., 2012]. Based on these findings, we hypothesize that increasing runoff from Greenland could decrease heat loss from subsurface waters, which could favor the warming of the WGIW in Baffin Bay.

To test our hypothesis, we set up eight freshwater sensitivity experiments using the ocean‐sea ice model Nucleus for European Modelling of the Ocean (NEMO) [Madec and the Nucleus for European Modelling of the Ocean team, 2008] for a wide range of meltwater discharge (Figure 1b). Icebergs also contribute to the Greenland ice sheet discharge into Baffin Bay [Tang et al., 2004]. However, due to the numerical cost involved in coupling in an iceberg model, combined with the fact that most of the iceberg melt will occur within the boundary current (i.e., same as for the runoff we apply) or south of Davis Strait [Tang et al., 2004], we begin examining this question without directly including an iceberg model.