Sea level trends at locations of the United States with more than 100 years of recording
Description
Observed Trends (Average of U.S. Stations with >100 Years of Record) By analyzing over 100 years of data from tide gauges (Relative Sea Level, RSL) and GPS stations (Vertical Land Motion, VLM) across the United States, the following patterns emerge (Table 1 observed trends for individual stations, Table 2 summary of observed trends).
Files
Steps to reproduce
Measurements from two complementary time series: tide gauges and GPS To analyze sea level changes, we combine measurements from two complementary time series: tide gauges and GPS. Tide Gauges – Relative Sea Level (RSL) Tide gauges provide the relative monthly mean sea level (MSL), denoted y(t), measured relative to the local land. The record spans t_s ≤ t ≤ t_e. A least‑squares fit—linear or parabolic—gives: RSL trend (slope), b_y, in mm yr⁻¹ (positive if sea level is rising relative to the land). RSL acceleration, a_y, in mm yr⁻². GPS – Vertical Land Motion (VLM) GPS stations measure the absolute vertical position z(t) of the land surface over recent decades. From the position time series we obtain: Recent uplift rate, b_{z,e}, in mm yr⁻¹ (positive for uplift, negative for subsidence) evaluated near t_e. Uplift at the start of the record, b_{z,s}, interpreted as the glacial isostatic adjustment Peltier VM4 past (GIA) contribution at t_s. The uplift acceleration is then estimated as: a_z = (b_{z,e} - b_{z,s}) / (t_e - t_s) [mm yr⁻²]. Combining to Obtain Absolute Sea Level (ASL) Absolute sea level change x(t) is the sum of the relative sea level and the vertical land motion: x(t) = y(t) + z(t). Consequently, the absolute sea level trend and acceleration are: b_x = b_y + b_z, a_x = a_y + a_z, where b_z is taken as the appropriate land‑motion rate (e.g., b_{z,e} for the modern trend), and a_z is the land‑motion acceleration defined above. Thus, by merging tide‑gauge relative sea levels with GPS‑derived vertical land velocities, we separate the land‑movement signal from the true ocean‑volume change, yielding the absolute sea‑level evolution. sea level data analysis and supporting data from sealevel.info GPS positioning data from https://geodesy.unr.edu/
Institutions
- Independent