Offsets in tide-gauge reference levels detected by satellite altimetry: ten case studies

Abstract

Comparing measurements of absolute sea level by satellite altimetry and relative sea level by a tide gauge can reveal errors in either measurement system. Combining the measurements can determine vertical land motion (VLM) at the tide gauge. We here discuss ten case studies in which a tide gauge has likely experienced a small ($$\le 10$$ ≤ 10 cm), discontinuous offset in the vertical, suggesting inadvertent loss of reference-level stability. Proper interpretation of offsets is helped if independent VLM measurements from nearby geodetic stations are available. In two cases, earthquake-induced VLM cannot be ruled out, although it appears unlikely. Offsets as small as 1–2 cm can be detected when both altimeter and tide gauge successfully observe the same ocean signal. This is most likely to occur for tide gauges located on small, open-ocean islands. Tide gauges near large land masses are typically more challenging owing to inadequacies of satellite altimetry near land and to differences between coastal and open-ocean sea levels. The case studies highlight the utility of satellite altimetry for tide-gauge quality control.

Improved capabilities of global ocean reanalyses for analysing sea level variability near the Atlantic and Gulf of Mexico Coastal U.S.

“…One interesting difference between the tide gauge and altimetry trends is in the western Gulf of Mexico where the former has larger trends, which is explained by the different reference frames of these observations (see Section 2). Places where the tide gaugemeasured trends are larger than the altimetry trends are likely to have experienced land subsidence (Kolker et al, 2011;Wöppelmann and Marcos, 2016;Ray et al, 2023), which is the case around many parts of the Texas and Louisiana Coasts. For example, during the 27-yr period, 26.2 cm of sea level rise was measured by the Grand Isle tide gauge but only 13.8 cm according to nearby altimetry observations, which are trends respectively equivalent to 9.70 mm/yr and 5.11 mm/ yr.…”

Non‐Linear Vertical Land Motion of Coastal Chile and the Antarctic Peninsula Inferred From Combining Satellite Altimetry, Tide Gauge and GPS Data

“…It is well known that ALT-TG records may have errors due to RSL datum shifts due to the instability of vertical reference level as the equipment changes (e.g., Ray et al, 2023;Woodworth et al, 2017;Wöppelmann et al, 2008). We have the potential to estimate these as pseudo co-seismic jumps within our framework.…”