Geodetic Calibration of Arctic Pressure Tide Gauges and Diagnosis of Density-Related Biases From Two Decades of GNSS-IR Altimetry

Abstract

Long-term coastal sea-level monitoring in polar regions relies on bottom-mounted pressure tide gauges (PTGs), which are less vulnerable to sea-ice damage but remain difficult to reference to a stable vertical datum. In addition, conventional pressure-to-height conversion commonly assumes constant seawater density, potentially introducing steric biases in dynamic Arctic estuaries. This study develops a nonintrusive geodetic calibration framework for Arctic PTGs using two decades of global navigation satellite system interferometric reflectometry (GNSS-IR) altimetry. Continuous signal-to-noise ratio observations from the TUKT GNSS station in the Canadian Arctic during 2003–2023 were processed to retrieve geometric sea levels during open-water seasons and evaluate a collocated submerged PTG. The GNSS-IR/PTG comparison reveals a persistent datum offset of −0.111 m. After the 2015 receiver modernization, retrieval precision stabilized below 5 cm root mean square error, supporting GNSS-IR as an independent geometric constraint for remote tide-gauge calibration. The residuals further show a repeatable nonlinear intraseasonal decline, inconsistent with simple monotonic datum drift. Regional river-level and ocean-temperature records suggest that this pattern is associated with early-summer halosteric contraction, a midsummer thermosteric rebound, and autumn cooling-induced thermosteric contraction. These results demonstrate that long-term GNSS-IR altimetry can support geodetic calibration of Arctic PTGs and provide diagnostic information on density-related biases in pressure-derived sea-level records, thereby improving the vertical consistency of polar observing networks where repeated leveling is logistically constrained.