Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation
Abstract In Southeast Alaska (SE-AK), rapid ground uplift of up to 3 cm/yr has been observed associated with post-Little Ice Age glacial isostatic adjustment (GIA). Geodetic techniques such as global navigation satellite system (GNSS) and absolute gravimetry have been applied to monitor GIA since th...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2022-07-01
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| Series: | Earth, Planets and Space |
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| Online Access: | https://doi.org/10.1186/s40623-022-01666-7 |
| _version_ | 1818502786346647552 |
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| author | Kazuhiro Naganawa Takahito Kazama Yoichi Fukuda Satoshi Miura Hideaki Hayakawa Yusaku Ohta Jeffrey T. Freymueller |
| author_facet | Kazuhiro Naganawa Takahito Kazama Yoichi Fukuda Satoshi Miura Hideaki Hayakawa Yusaku Ohta Jeffrey T. Freymueller |
| author_sort | Kazuhiro Naganawa |
| collection | DOAJ |
| description | Abstract In Southeast Alaska (SE-AK), rapid ground uplift of up to 3 cm/yr has been observed associated with post-Little Ice Age glacial isostatic adjustment (GIA). Geodetic techniques such as global navigation satellite system (GNSS) and absolute gravimetry have been applied to monitor GIA since the last 1990s. Rheological parameters for SE-AK were determined from dense GNSS array data in earlier studies. However, the absolute gravity rate of change observed in SE-AK was inconsistent with the ground uplift rate, mainly because few gravity measurements from 2006 to 2008 resulted in imprecise gravity variation rates. Therefore, we collected absolute gravity data at six gravity points in SE-AK every June in 2012, 2013, and 2015, and updated the gravity variation rate by reprocessing the absolute gravity data collected from 2006 to 2015. We found that the updated gravity variation rate at the six gravity points ranged from −2.05 to −4.40 $$\upmu$$ μ Gal/yr, and its standard deviation was smaller than that reported in the earlier study by up to 88 %. We also estimated the rheological parameters under the assumption of the incompressible Earth to explain the updated gravity variation rate, and their optimal values were determined to be 55 km and $$1.2 \times 10^{19}$$ 1.2 × 10 19 Pa s for lithospheric thickness and upper mantle viscosity, respectively. These optimal values are consistent with those independently obtained from GNSS observations, and this fact indicates that absolute gravimetry can be one of the most effective methods in determining sub-surface structural parameters associated with GIA accurately. Moreover, we utilized the gravity variation rates for estimating the ratio of gravity variation to vertical ground deformation at the six gravity points in SE-AK. The viscous ratio values were obtained as −0.168 and −0.171 $$\upmu$$ μ Gal/mm from the observed data and the calculated result, respectively. These ratios are greater (in absolute) than those for other GIA regions (−0.15 to −0.16 $$\upmu$$ μ Gal/mm in Antarctica and Fennoscandia), because glaciers in SE-AK have melted more recently than in other regions. Graphical Abstract |
| first_indexed | 2024-12-10T21:15:05Z |
| format | Article |
| id | doaj.art-8e9f4bb1cefa4166b97a526040b19e81 |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-12-10T21:15:05Z |
| publishDate | 2022-07-01 |
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| series | Earth, Planets and Space |
| spelling | doaj.art-8e9f4bb1cefa4166b97a526040b19e812022-12-22T01:33:20ZengSpringerOpenEarth, Planets and Space1880-59812022-07-0174112710.1186/s40623-022-01666-7Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimationKazuhiro Naganawa0Takahito Kazama1Yoichi Fukuda2Satoshi Miura3Hideaki Hayakawa4Yusaku Ohta5Jeffrey T. Freymueller6Graduate School of Science, Kyoto UniversityGraduate School of Science, Kyoto UniversityGraduate School of Science, Kyoto UniversityResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityInstitute for Cosmic Ray Research, the University of TokyoResearch Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku UniversityGeophysical Institute, University of Alaska FairbanksAbstract In Southeast Alaska (SE-AK), rapid ground uplift of up to 3 cm/yr has been observed associated with post-Little Ice Age glacial isostatic adjustment (GIA). Geodetic techniques such as global navigation satellite system (GNSS) and absolute gravimetry have been applied to monitor GIA since the last 1990s. Rheological parameters for SE-AK were determined from dense GNSS array data in earlier studies. However, the absolute gravity rate of change observed in SE-AK was inconsistent with the ground uplift rate, mainly because few gravity measurements from 2006 to 2008 resulted in imprecise gravity variation rates. Therefore, we collected absolute gravity data at six gravity points in SE-AK every June in 2012, 2013, and 2015, and updated the gravity variation rate by reprocessing the absolute gravity data collected from 2006 to 2015. We found that the updated gravity variation rate at the six gravity points ranged from −2.05 to −4.40 $$\upmu$$ μ Gal/yr, and its standard deviation was smaller than that reported in the earlier study by up to 88 %. We also estimated the rheological parameters under the assumption of the incompressible Earth to explain the updated gravity variation rate, and their optimal values were determined to be 55 km and $$1.2 \times 10^{19}$$ 1.2 × 10 19 Pa s for lithospheric thickness and upper mantle viscosity, respectively. These optimal values are consistent with those independently obtained from GNSS observations, and this fact indicates that absolute gravimetry can be one of the most effective methods in determining sub-surface structural parameters associated with GIA accurately. Moreover, we utilized the gravity variation rates for estimating the ratio of gravity variation to vertical ground deformation at the six gravity points in SE-AK. The viscous ratio values were obtained as −0.168 and −0.171 $$\upmu$$ μ Gal/mm from the observed data and the calculated result, respectively. These ratios are greater (in absolute) than those for other GIA regions (−0.15 to −0.16 $$\upmu$$ μ Gal/mm in Antarctica and Fennoscandia), because glaciers in SE-AK have melted more recently than in other regions. Graphical Abstracthttps://doi.org/10.1186/s40623-022-01666-7Absolute gravity changeSoutheast AlaskaRheological parameterMantle viscosityLithospheric thicknessPresent-day ice melting |
| spellingShingle | Kazuhiro Naganawa Takahito Kazama Yoichi Fukuda Satoshi Miura Hideaki Hayakawa Yusaku Ohta Jeffrey T. Freymueller Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation Earth, Planets and Space Absolute gravity change Southeast Alaska Rheological parameter Mantle viscosity Lithospheric thickness Present-day ice melting |
| title | Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation |
| title_full | Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation |
| title_fullStr | Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation |
| title_full_unstemmed | Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation |
| title_short | Updated absolute gravity rate of change associated with glacial isostatic adjustment in Southeast Alaska and its utilization for rheological parameter estimation |
| title_sort | updated absolute gravity rate of change associated with glacial isostatic adjustment in southeast alaska and its utilization for rheological parameter estimation |
| topic | Absolute gravity change Southeast Alaska Rheological parameter Mantle viscosity Lithospheric thickness Present-day ice melting |
| url | https://doi.org/10.1186/s40623-022-01666-7 |
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