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).
Historically, the formation of a northern and southern [ice] arch has been observed in Robeson Channel and Smith Sound, respectively (Fig. 1) (Vincent, 2019).