Sea-level fluctuations during the historical period in Gomso Bay, Korea

Historical sea-level changes in Gomso Bay, the tectonically stable “far-field” area, in the midwestern Korean Peninsula were inferred based on old documents concerning salt production and shipping routes. The sea-level in the 570s CE was similar to that at present, fell at some time around the 1530s CE, rose in the 1750s CE, and rose more in the 1790s CE. The 1-m-long sediment core QJB-30 recovered from the Gomso Bay area shows a marine unit, paleosol unit, and another marine unit in stratigraphic order, supporting this interpretation. The soil formation in the paleosol unit appeared to progress at the location of the core while sea-level was lowered around the 1500s and 1600s CE. Given that the tidal flat is widely distributed in this bay, subtle sea-level fluctuations could appear largely due to the local differences in topographic gradients and the overall shape of the bay. This study also shows that sea-level rise began earlier than the end of the Little Ice Age (1850 CE). The most likely explanation for this is that meltwater from the Greenland Ice Sheet in the early 1700s CE caused sea-level rise around the Korean Peninsula due to sea-level fingerprint effects. Old documents describing coastal areas are important sources for reconstructing historical sea-levels, and they inform us about changes both in the natural environment and in human activity.