Annual mean absolute sea levels reconstructed from gauged relative sea levels by removing land subsidence at Galveston Pier 21, Texas and in Baltimore Inner Harbor, Maryland

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Annual mean absolute sea levels (AMASLs) from tide gauge records can be fundamental data for understanding global glaciers' melting and sea water expanding with global warming. AMASLs only can be reconstructed well from gauged relative sea levels by removing land subsidence (LS) if reliable LS data is available at tide gauge locations. LS at tide gauge locations can consider three components: tectonic subsidence (TS) from basement rocks, primary consolidation subsidence (PCS) of compressible coastal aquifer systems due to subsurface fluid withdrawal and creep subsidence (CS) of the same aquifer systems without over-consolidation due to geohistorical overburden pressure. It is assumed that at the two tide gauge locations TS is linear with time, PCS is piecewise linear with time, and CS decreases linearly with logarithmic time. LS rate at Galveston Pier 21 was estimated to be 3.54 mm/a during 1909-37, 6.08 mm/a during 1937-83, and 3.50 mm/a since 1983. LS rate at Baltimore Inner Harbor was estimated to be 1.93 mm/a during 1903-1920, -3.15 mm/a during 1920-26, 4.13 mm/a during 1926-47, 1.74 mm/a during 1947-57, -1.91 mm/a during 1957-62, 1.57 mm/a during 1962-1980, 2.17 mm/a during 1980 to 1992, and 1.57 mm/a since 1992. After removing LS from gauged relative sea levels, AMASLs are reconstructed at Galveston Pier 21 and in Baltimore Inner Harbor. Constant absolute sea level rise rate before 1992 and acceleration since 1992 were found to be 1.10+-0.19 mm/a and 0.270 mm/a2 at Galveston Pier 21 and 1.11+-0.10 mm/a and 0.254 mm/a2 at Baltimore Inner Harbor, respectively.