Total meltwater volume since the Last Glacial Maximum and viscosity structure of Earth's mantle inferred from relative sea level changes at Barbados and Bonaparte Gulf and GIA-induced J2

Masao Nakada, Jun'ichi Okuno, Yusuke Yokoyama

研究成果: Contribution to journalArticle査読

18 被引用数 (Scopus)

抄録

Inference of globally averaged eustatic sea level (ESL) rise since the Last Glacial Maximum (LGM) highly depends on the interpretation of relative sea level (RSL) observations at Barbados and Bonaparte Gulf, Australia, which are sensitive to the viscosity structure of Earth's mantle. Here we examine the RSL changes at the LGM for Barbados and Bonaparte Gulf (RSLBar, BonL ), differential RSL for both sites (ΔRSLBar, BonL ) and rate of change of degree-two harmonics of Earth's geopotential due to glacial isostatic adjustment (GIA) process (GIA-induced J˙2) to infer the ESL component and viscosity structure of Earth's mantle. Differential RSL, ΔRSLBar, BonL and GIA-induced J˙2 are dominantly sensitive to the lower-mantle viscosity, and nearly insensitive to the upper-mantle rheological structure and GIA ice models with an ESL component of about (120-130) m. The comparison between the predicted and observationally derived ΔRSLBar, BonL indicates the lower-mantle viscosity higher than ~2 × 1022 Pa s, and the observationally derived GIA-induced J˙2 of -(6.0-6.5) × 10-11 yr-1 indicates two permissible solutions for the lower mantle, ~1022 and (5-10) × 1022 Pa s. That is, the effective lower-mantle viscosity inferred from these two observational constraints is (5-10) × 1022 Pa s. The LGM RSL changes at both sites, RSLBarL and RSLBonL, are also sensitive to the ESL component and upper-mantle viscosity as well as the lower-mantle viscosity. The permissible upper-mantle viscosity increases with decreasing ESL component due to the sensitivity of the LGM sea level at Bonaparte Gulf (RSLBon L ) to the upper-mantle viscosity, and inferred upper-mantle viscosity for adopted lithospheric thicknesses of 65 and 100 km is (1-3) × 1020 Pa s for ESL~130m and (4-10) × 1020 Pa s for ESL~125 m. The former solution of (1-3) × 1020 Pa s is consistent with the inferences from the postglacial differential RSL changes in the Australian region and also inversion study of far-field sea-level data. The inference of the viscosity structure based on these four observational constraints is, however, relatively insensitive to the viscosity structure of D" layer.

本文言語英語
ページ(範囲)1237-1253
ページ数17
ジャーナルGeophysical Journal International
204
2
DOI
出版ステータス出版済み - 2 1 2016

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

フィンガープリント 「Total meltwater volume since the Last Glacial Maximum and viscosity structure of Earth's mantle inferred from relative sea level changes at Barbados and Bonaparte Gulf and GIA-induced J<sub>2</sub>」の研究トピックを掘り下げます。これらがまとまってユニークなフィンガープリントを構成します。

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