New paper finds sea levels in Japan were 2 meters higher 4,000 years ago, when 'melting of the Antarctic ice sheet ended'

A paper published today in Geophysical Research Letters finds that the sea level in northern Japan was 2 meters higher than the present 4,000 years ago. The authors conclude, "Given that meltwater contributions [increase in sea level from melting ice] from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by 4,000 years ago."

GEOPHYSICAL RESEARCH LETTERS, doi:10.1029/2012GL051983

Holocene sea-level change and Antarctic melting history derived from geological observations and geophysical modeling along the Shimokita Peninsula, northern Japan.

Key Points

• Sea-level observations and glacio-hydro-isostatic modeling were coupled
• Last deglaciation of Antarctica was ceased largely by 3-4 ka
• Recent accerelation of Antarctic melting is likely due to anthoropogenic origin

Authors:

Yusuke Yokoyama

Jun'ichi Okuno

Yosuke Miyairi

Stephen Obrochta

Nobuhiro Demboya

Yoshinori Makino

Hodaka Kawahata

A Mid to Late Holocene sea-level record based on combined geomorphological, geological and micropaleontological observations was obtained from well-developed wave cut benches subaerially exposed along the Shimokita Peninsula, northern Japan. Results indicate that the benches were formed during mid to late Holocene sea-level transgressions, reaching a maximum highstand level [high point of sea level] of 2 m above present at about 4,000 years ago. This timing corresponds to an abrupt, order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal Mutsu Bay. In addition, glacio-hydro-isostatic adjustment due to crustal deformation in response to postglacial sea-level rise was modeled, and results are consistent with the reconstructed local 2 m highstand. Given that meltwater contributions from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by 4,000 years ago.