Sea-level change mechanisms (sketch)

Sketches outlining the solid-Earth induced change of sea level over different time periods, covering elastic (instantaneous), viscous (thousand to hundred thousand years), and mantle convection (Million to Billion years) time scales. Shown are the solid Earth and oceans (filled areas) and their surfaces after an applied change to the system (lines). On the shortest time scales, the solid Earth deforms elastically in response to an imposed load: an ice sheet uplifts the ground near areas of mass loss and depresses the ocean basins, which gain mass. The sea surface drops near the mass loss because the diminished ice sheet gravitationally attracts less seawater. Relative to the ground surface, sea-level drops near melting ice, but rises faster than average over the rest of the ocean. Following glacial unloading, Earth deforms viscously on time scales of 103–105 yr as the mantle flows back into the depressed region. This uplifts the region near the former ice sheet (locally causing relative sea-level drop) and depresses the surrounding peripheral forebulge. If the forebulge collapses beneath the sea surface, the added basin volume causes far-field (eustatic) sea-level drop. On time scales of 106 yr and longer, solid Earth processes associated with plate tectonics and mantle dynamics dominate sea-level change (Harrison, 1990; Miller et al., 2005). Shown here are the major processes that can elevate global average (eustatic) sea level (and depress it when acting oppositely). Global sea level rises when the “container” volume of the ocean basins decreases, which can have multiple reasons. Sea level also rises if water exchange with the deep mantle becomes imbalanced.

  • Creator: Clint P. Conrad
  • This version: 27.10.2021
  • License: Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
  • Specific citation: This graphic by Clint Conrad based on Conrad (2013) is available via the open-access s-Ink repository.
  • Related reference: Conrad, C.P. (2013), The solid earth’s influence on sea level, Geological Society of America Bulletin, 125, 1027-1052, doi:10.1130/B30764.1.
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