Progressive changes in geometry and dynamics of the Northern Pine Island Ice Shelf, West Antarctica

Abstract. The Pine Island Ice Shelf can be analysed within three distinct sectors: northern, southern, and central. Dynamics within the Northern Pine Island Ice Shelf (N-PIIS) remain less understood than those of the Central Pine Island Ice Shelf. Using satellite imagery, reanalysis datasets, and in situ observations, we examined changes in ice-front position, velocity, thickness, rift propagation, and polynya activity across the N-PIIS since 1973. Overall, the ice-shelf area has decreased, and surface elevation data indicate ongoing thinning. Grounded ice velocities have remained largely stable, although localized accelerations occurred near the floating portion of the N-PIIS and the grounded section of Velasco Glacier. Several former pinning points have disappeared, and three polynyas have developed around the ice shelf, suggesting enhanced ocean-ice interaction. Our observations document continued thinning, frontal retreat, pinning-point loss, and episodic polynya formation at the N-PIIS. While large-scale dynamic acceleration is limited, these changes suggest a progressive reduction in structural stability and increased sensitivity to oceanic and atmospheric forcing. This study provides critical new insights into the evolving stability of the N-PIIS and highlights the importance of continued monitoring to anticipate potential disintegration.