- The first two paragraphs of the introduction are annoted. Continue and refine annotation.
- The Petermann 2015 expedition to Petermann Fjord and adjacent Hall Basin recovered a transect of cores, extending from Nares Strait to underneath the 48 km long ice tongue of Petermann glacier, offering a unique opportunity to study ice–ocean–sea ice interactions at the interface of these realms. First results suggest that no ice tongue existed in Petermann Fjord for large parts of the Holocene, raising the question of the role of the ocean and the marine cryosphere in the collapse and re-establishment of the ice tongue. Here we use a multi-proxy approach (sea-ice-related biomarkers, total organic carbon and its carbon isotopic composition, and benthic and planktonic foraminiferal abundances) to explore Holocene sea ice dynamics at OD1507-03TC-41GC-03PC in outer Petermann Fjord. Our results are in line with a tight coupling of the marine and terrestrial cryosphere in this region and, in connection with other regional sea ice reconstructions, give insights into the Holocene evolution of ice arches and associated landfast ice in Nares Strait.
- Nares Strait, connecting the Lincoln Sea to the northern Baffin Bay, is an important conduit for sea ice, freshwater, and heat between the Arctic Ocean and the western North Atlantic.
- In the winter of 2006/2007 both ice arches failed to form for the first time in recorded history, causing sea ice to remain mobile in Nares Strait year-round (Kwok et al., 2010; Vincent, 2019) (Fig. 2, Supplement Fig. S1).
- The observed changes in Nares Strait sea ice dynamics likely have significant consequences for the export of multi-year sea ice from the Lincoln Sea and long-term Arctic sea ice loss (Kwok et al., 2010; Moore et al., 2021; Vincent, 2019) (Fig. 2).
- Additionally, the formation of the southern ice arch in Smith Sound is crucial for the annual opening of the North Water Polynya (NOW) (Fig. 1) and the formation of landfast sea ice in Nares Strait (Barber et al., 2001).
- The annual flux of freshwater through Nares Strait, in liquid and solid form, heavily depends on the seasonal formation of ice arches (Kwok et al., 2010; Münchow, 2016; Rasmussen et al., 2010).
- Ice arches form when drift ice converges in a narrow passage between two landmasses.
- In Nares Strait their formation [ice arches] depends primarily on the sea ice thickness, local wind stresses, and atmospheric temperatures (Barber et al., 2001; Kwok et al., 2010; Samelson et al., 2006).
- Ice arching inhibits sea ice export from the Arctic Ocean and allows the formation of landfast ice in Nares Strait, consisting of a mixture of multi-year drift ice, originating from the Arctic Ocean, and locally formed first-year ice (Kwok, 2005; Kwok et al., 2010).
- Historically, the formation of a northern and southern [ice] arch has been observed in Robeson Channel and Smith Sound, respectively (Fig. 1) (Vincent, 2019).
- In recent decades, however, changes in the ice arch configuration suggest a transition in Nares Strait sea ice dynamics.
- Between 1979 and 2019, Nares Strait was blocked for sea ice passage on average 161 d per season with a consistent decrease of 2.1 d yr−1 throughout this period (Vincent, 2019).
- This is associated with a shift from a prominent southern ice arch towards increased importance of the northern arch (Vincent, 2019).
- The water column in Nares Strait is characterized by cold and fresh Polar Water (PW) in the upper 50–100 m with warmer and more saline modified Atlantic Water (AW) below, separated by a strong halocline (Johnson et al., 2011; Münchow et al., 2014).
- Under landfast sea ice conditions, Ekman transport causes eastward displacement of cold and fresh PW [Polar Water] [in Nares Strait] towards the Greenland coast (Rabe et al., 2012; Shroyer et al., 2015, 2017).
- Conversely, mobile sea ice leads to westward Ekman transport of PW [Polar Water] and upwelling of AW [Atlantic Water] in the east, increasing the oceanic heat flux to fjord systems along the Greenland coast of Nares Strait (Münchow et al., 2007; Shroyer et al., 2017).
- Outlet glaciers draining into fjords in the north and northeast of Greenland commonly terminate in a floating ice tongue of variable length, with three glaciers terminating in an ice tongue > 10 km (Hill et al., 2017).
- One such glacier is Petermann Glacier (PG), draining about 4 % of the Greenland Ice Sheet (GrIS) (based on area of the drainage basin; Rignot and Kanagaratnam, 2006) into Hall Basin in Nares Strait (Fig. 1).
- Large calving events of the PG [Petermann Glacier] floating ice tongue in 2010 and 2012 (Johannessen et al., 2013; Rückamp et al., 2019) were associated with a 10 % acceleration of the glacier (Rückamp et al., 2019).
- Interestingly, the 2010 calving event occurred at the end of a 4-year period with no or little landfast ice in Nares Strait, which was associated with earlier breakup of landfast ice (Fig. 2).
- The smaller calving event in 2012, on the other hand, followed the re-establishment of extensive landfast ice in Nares Strait in 2011 (Fig. 2).
- Although the calving events have attracted considerable attention, submarine melting of the ice tongue accounts for 80 % of the mass loss at PG [Petermann Glacier], making it particularly sensitive to ice–ocean interactions (Cai et al., 2017; Münchow et al., 2014; Rignot and Steffen, 2008; Rückamp et al., 2019).