Relative sea level change from tide gauge records of western North America

Abstract

Negligible success of investigators in relating tide gauge records of the west coast of North America to eustatic changes of sea level is the result of tectonic movements of the land reference level beneath the tide gauges. The vertical tectonic movements are caused by horizontal movements of oceanic crustal plates. Sinking of 12 mm/yr at Cordova, Alaska, is associated with intense subduction at the east end of the Aleutian Trench; rising by 6 mm/yr at Skagway may be caused by resistance to lateral crustal movement toward the filled trench; rising of 1 mm/yr in southern Alaska (uplift above slow subduction); little vertical movement between Sitka and Mendocino Fracture Zone (translation and slow subduction including fracture zones and thick sediments); sinking of 1 mm/yr west of the San Andreas fault (translation); and sinking of 2 mm/yr along northwestern Mexico (effects of cooling of late rifted crust and only diagonal subduction). Superimposed on this tectonism due to plate motion is broad scale isostatic adjustment (both rise and fall) resulting from deglaciation. Removal of rigid plate motion deltas helps resolve subplate tectonic processes. Higher‐frequency (0.05–0.5 cpy) sea level changes as well as large‐scale pressure fluctuations and wind stress events are associated with El Niño/Southern Oscillation. An apparent increase in relative sea level rise near 1935, also observed in other regions, remains to be explained.