Observing tidal effects on the dynamics of the Ekström Ice Shelf with focus on quarterdiurnal and terdiurnal periods

• Published in: Journal of Glaciology
• Main Authors: Tanja Fromm, Vera Schlindwein, Veit Helm, Vera Fofonova
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2023
• Subjects: Antarctic glaciology; ice/ocean interactions; ice shelves; ice velocity; seismology; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Antarctic; Dronning Maud Land; Ekström Ice Shelf; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves; Journal of Glaciology
• Online Access: https://doi.org/10.1017/jog.2023.4; https://doaj.org/article/70edc3c2280040ca9b11a4d9e50cde56

Antarctica's ice shelves stabilize the ice sheet and, therefore, understanding processes affecting the mass budgets of ice shelves is important for estimating grounded ice loss. To study the ice shelf dynamics, we analyzed seismological and GNSS data from the Ekström Ice Shelf in Dronning Maud Land. We extracted probabilistic power spectral densities (PPSD) in the frequency band 3.4–6.8 Hz, typical of icequakes, from seismological data and observed pronounced signals in the PPSD with near 3 and 4 cycles per day (cpd) corresponding to tidal overharmonics, in addition to the main tidal constituents near 1 and 2 cpd. GNSS data reveal the same components in ice flow speed but not in vertical displacements. Generally, tide-induced grounding line migration modulates the flow velocity of an entire ice shelf. We find that this velocity modulation causes the increased icequake activity in the tidal overharmonics with 3 and 4 cpd in an ice shear zone where the flow velocity drops to nearly zero.