NAD83v70VG: a new national crustal velocity model for Canada

Abstract

A national-scale crustal velocity model has been developed for Canada as part of the current realisation of NAD83(CSRS), delivered as a set of 3 national grids, for each of the North, East and Up (N, E and U) components. It is used to propagate coordinates to different reference epochs, and to support scientific studies such as natural hazards, climate change, and groundwater change. The previous velocity model was based on continuous and campaign GPS data between 1994 and 2011.3. The new model includes new stations in key areas, six more years of data (to the end of 2017), and newly reprocessed historical data using the latest software and GPS products. We include data from continuous GPS sites in Canada, the northern portions of the US, all of Greenland, and a set of globally distributed sites used to define the reference frame; and from repeated high accuracy campaign surveys in Canada. A new type of model is introduced for the vertical grid. It incorporates GPS observations with the crustal uplift predictions of Glacial Isostatic Adjustment (GIA) and elastic rebound models, which are especially important in areas with sparse coverage. Gridded uncertainty estimates are provided for each component of NAD83v70VG.

Postglacial sea-level lowstand on Cumberland Peninsula, Baffin Island, Nunavut

“…These include submerged wave-cut terraces, deltas, beach ridges, incised bedrock, barrier platforms, flooded estuaries and salt marshes, and flooded isolated basins (e.g., England and Andrews 1973;Shaw and Forbes 1995;Forbes et al 1995Forbes et al , 2014Bell et al 2003;Shaw 2005;Billy et al 2018). Relict shoreline features combined with Global Positioning System (GPS) monitoring stations co-located with tide gauges are important for constraining regional GIA and RSL models and provide the data required to construct RSL curves for the Canadian Arctic (Forbes et al 2004;Simon et al 2014;Robin et al 2020;James et al 2021). As there has been limited validation of the most recent GIA model in the eastern Arctic, the submerged shoreline dataset presented in this paper offers an opportunity for comparison and possible refinement of the model in a region dominated locally at the LGM by alpine ice, between the Laurentide and Greenland ice sheets.…”

Relative sea-level projections for Canada based on the IPCC Fifth Assessment Report and the NAD83v70VG national crustal velocity model

“…Over much of Canada, the contribution of vertical land motion to projected relative sea-level is sea-level fall ( Figure 2). (Robin et al, 2020) in millimetres per year. The hinge line (thick black line) is the zero contour between uplift and subsidence.…”

“…Contribution of vertical land motion to projected sea-level change at 2100. The contribution is determined by converting uplift rates (Robin et al, 2020) to equivalent relative sea-level change rates, taking into account changes to the geoid (James et al, 2014), and scaling by the elapsed time.…”

“…The sea-level projections are based on a national model of vertical crustal motion derived from GPS measurements (Robin et al, 2020). For the purposes of establishing national geodetic reference frames, GPS antenna are usually installed on monuments fixed to bedrock, and in some cases to long-established masonry buildings.…”

“…The relative sea-level projections given here are based on the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) (Church et al, 2013a, b) and on the NAD83v70VG model of vertical land motion for Canada based on GPS observations (Robin et al, 2020). The vertical land motion model was augmented with the predictions of glacial isostatic adjustment (GIA) models to interpolate between spatially sparse observation sites, which is particularly important in the north.…”