Identifying Geographical Patterns of Transient Deformation in the Geological Sea Level Record. Issue 7 (20th July 2022)

• Record Type: Journal Article
• Authors: Simon, K. M.; Riva, R. E. M.; Broerse, T.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 7(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-07-20
• Subjects: glacial isostatic adjustment -- transient mantle deformation -- relative sea level; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2021JB023693
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: In this study, we examine the effect of transient mantle creep on the prediction of glacial isostatic adjustment (GIA) signals. Specifically, we compare predictions of relative sea level (RSL) change from GIA from a set of Earth models in which transient creep parameters are varied in a simple Burgers model to a reference case with a Maxwell viscoelastic rheology. The model predictions are evaluated in two ways: first, relative to each other to quantify the effect of parameter variation, and second, for their ability to reproduce well‐constrained sea level records from selected locations. Both the resolution and geographic location of the RSL observations determine whether the data can distinguish between model cases. Model predictions are most sensitive to the inclusion of transient mantle deformation in regions that are near‐field and peripheral relative to former ice sheets. This sensitivity appears particularly true along the North American west coast in the region of the former Cordilleran Ice Sheet, which experienced rapid sea‐level fall following deglaciation between 14 and 12 kyr BP. Relative to the Maxwell case, Burgers models better reproduce this rapid phase of regional postglacial sea‐level fall. As well, computed goodness‐of‐fit values in this region show a clear preference for models where transient deformation is present in the whole or lower mantle, and for models where the rigidity of the Kelvin element is weakened relative to the rigidity of the Maxwell element. In contrast, model predictions of relative sea‐level change in the far‐field show weak sensitivity to the inclusion of transient deformation. Plain Language Summary: In this study, we compare glacial isostatic adjustment (GIA) model predictions using two different Earth model types: Maxwell and Burgers models. Maxwell models are commonly used in GIA studies and employ a time‐invariant (steady‐state) form of mantle creep. Burgers models, on the other hand, allow for time‐varying mantle deformation and include both steady‐state and transient components of mantle creep. To evaluate the models, the predictions from both model types are compared to high quality records of relative sea level (RSL) change over the last several thousand years. Burgers models that include transient (time‐varying) mantle deformation often fit the RSL data as well as, or better, than the Maxwell models. In particular, the fit between predictions and data is improved in regions that were beneath or near former ice sheets, for example, along the west coast of North America. This result suggests that transient mantle deformation should be considered an additional process of interest in GIA models, especially in regions near the former ice sheets. Key Points: We compare glacial isostatic adjustment (GIA) model predictions with Maxwell and Burgers rheologies to relative sea level data Models with Burgers rheology can yield better fits to sea level data, particularly around the west coast of North America Transient deformation should be another process of interest in GIA models, especially in the near‐field