To plan for rising sea levels, coastal cities must know whether the ground under them is sinking or lifting and by how much. Scientists can estimate Vertical Land Motion (VLM) by subtracting satellite sea‑level data from tide‑gauge measurements. In complex coastlines, such as estuaries, this estimate may not perform well because local winds and river flow disturb the satellite measurements.

We analyzed 116 tide‑gauge sites from St. Lawrence River, Canada down to the Texas Coast. First, we averaged the best offshore satellite points for each gauge. Next, we removed the extra “noise” caused by nearby winds and river discharge. These two steps cut the typical error in VLM estimates almost in half—from 2.4 mm per year to 1.3 mm per year. The sharpest fixes came inside estuaries: at Trois‑Rivières, the error shrank from 8.5 mm to just 0.4 mm per year.