A relative sea-level history for Arviat, Nunavut, and implications for Laurentide Ice Sheet thickness west of Hudson Bay Karen M. Simon a,b, ⁎, Thomas S. James b,a , Donald L. Forbes c,d , Alice M. Telka e , Arthur S. Dyke f , Joseph A. Henton g a School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8P 5C2, Canada b Geological Survey of Canada—Pacific, Natural Resources Canada, Sidney, BC V8L 4B2, Canada c Geological Survey of Canada—Atlantic, Natural Resources Canada, Dartmouth, NS B2Y 4A2, Canada d Department of Geography, Memorial University, St. John's, NL A1B 3X9, Canada e Paleotec Services, Ottawa, ON K1R 5K2, Canada f Geological Survey of Canada—Northern, Natural Resources Canada, Ottawa, ON K1A 0E8, Canada g Canadian Geodetic Survey, Natural Resources Canada, Sidney, BC V8L 4B2, Canada abstract article info Article history: Received 19 September 2013 Available online 6 May 2014 Keywords: Kivalliq Radiocarbon dating Uplift rate Glacial isostatic adjustment Laurentide Ice Sheet Tyrrell Sea Thirty-six new and previously published radiocarbon dates constrain the relative sea-level history of Arviat on the west coast of Hudson Bay. As a result of glacial isostatic adjustment (GIA) following deglaciation, sea level fell rapidly from a high-stand of nearly 170 m elevation just after 8000 cal yr BP to 60 m elevation by the mid Holocene (~5200 cal yr BP). The rate of sea-level fall decreased in the mid and late Holocene, with sea level falling 30 m since 3000 cal yr BP. Several late Holocene sea-level measurements are interpreted to originate from the upper end of the tidal range and place tight constraints on sea level. A preliminary measurement of present- day vertical land motion obtained by repeat Global Positioning System (GPS) occupations indicates ongoing crustal uplift at Arviat of 9.3 ± 1.5 mm/yr, in close agreement with the crustal uplift rate inferred from the inferred sea-level curve. Predictions of numerical GIA models indicate that the new sea-level curve is best fit by a Laurentide Ice Sheet reconstruction with a last glacial maximum peak thickness of ~3.4 km. This is a 30–35% thickness reduction of the ICE-5G ice-sheet history west of Hudson Bay. © 2014 University of Washington. Published by Elsevier Inc. All rights reserved. Introduction The region west of Hudson Bay is near the centre of the former Laurentide Ice Sheet (LIS) (Dyke and Prest, 1987; Dyke, 2004). The history of the LIS is constrained by radiocarbon ages documenting the evolution of its areal extent, but few direct measurements of ice thick- ness exist inland from the margins of the former ice sheet. The thickness of the LIS is needed to determine its former volume in order to construct the global sea-level budget from the last glacial maximum to present- day (Peltier, 2004, 2009; Bassett et al., 2005; Tamisiea, 2011). Reliable models of past ice-sheet thickness are also necessary to reproduce observed present-day vertical and horizontal crustal motions from glacial isostatic adjustment (GIA), and thereby contribute to under- standing crustal deformation and earthquake occurrence (James and Bent, 1994; Argus et al., 1999; Milne et al., 2001; Mazzotti and Adams, 2005; Calais et al., 2006; Tiampo et al., 2012). Since few direct constraints on LIS ice thickness exist, its thickness history is often inferred from fitting the Earth's GIA response to available measurements of relative sea-level change (e.g., Tushingham and Peltier, 1991; Lambeck, 1993; Lambeck et al., 1998; Peltier, 2004; James et al., 2009). Observations of past and present-day sea-level change and vertical crustal motion are therefore important for inferring LIS history and estimating the maximum thickness of the ice sheet. Prior to this study, however, the relative sea-level history of the region west of the coast of central Hudson Bay was relatively poorly constrained, especially in the mid and late Holocene. Only eight radiocarbon- constrained relative sea-level measurements were available for this region, and of these, only two were late Holocene. In this paper, we present new radiocarbon ages and combine them with previously published ages to obtain an improved sea-level history for the region around Arviat (formerly Eskimo Point), Nunavut, on the west coast of Hudson Bay (Fig. 1). A preliminary measurement of the rate of present-day crustal uplift obtained from repeated Global Posi- tioning System (GPS) observations provides additional information on the ongoing GIA response at Arviat. We use the improved relative sea- level curve, as well as the present-day uplift rate, to constrain a GIA modelling sensitivity analysis that explores variations to ice-sheet thickness west of Hudson Bay in Peltier's (2004) ICE-5G reconstruction. The modelling analysis is consistent with the work of Lambert et al. (2006), Argus and Peltier (2010), and Mazzotti et al. (2011), which Quaternary Research 82 (2014) 185–197 ⁎ Corresponding author at: School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8P 5C2, Canada. E-mail address: ksimon@nrcan.gc.ca (K.M. Simon). http://dx.doi.org/10.1016/j.yqres.2014.04.002 0033-5894/© 2014 University of Washington. Published by Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Quaternary Research journal homepage: www.elsevier.com/locate/yqres