27 Jun 2023
 | 27 Jun 2023
Status: this preprint is currently under review for the journal TC.

Triggers of the 2022 Larsen B multi-year landfast sea ice break-out and initial glacier response

Naomi E. Ochwat, Ted A. Scambos, Alison F. Banwell, Robert S. Anderson, Michelle L. Maclennan, Ghislain Picard, Julia A. Shates, Sebastian Marinsek, Liliana Margonari, Martin Truffer, and Erin C. Pettit

Abstract. In late March 2011, landfast sea ice (hereafter, ‘fast ice’) formed in the northern Larsen B embayment and persisted continuously as multi-year fast ice until January 2022. In the 11 years of fast ice presence, the northern Larsen B glaciers developed extensive mélange areas and formed ice tongues that extended up to 16 km from their 2011 ice fronts. In situ measurements of ice speed on adjacent ice shelf areas spanning 2011 to 2017 show that the fast ice provided significant resistive stress to ice flow. Fast ice breakout began in January 2022, and was closely followed by retreat and break-up of both the glacier mélange and the adjacent ice tongue areas. We investigate the probable triggers for the loss of fast ice and document the initial upstream glacier responses. Our results suggest that the fast ice loss was linked to strong wave action (>1.5 m amplitude) with long period swells (>5 s) that reached the embayment simultaneously with the appearance of rifts in the ice. This coincided with a 12-year low in sea ice concentration in the northwestern Weddell Sea. Remote sensing data in the months following the fast ice break-out reveals an initial ice flow speed increase (up to 333 %), elevation loss (9 to 11 m), and rapid calving of floating and grounded ice for the three main glaciers Crane (11 km), Hektoria (25 km), and Green (18 km).

Naomi E. Ochwat et al.

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Naomi E. Ochwat et al.

Naomi E. Ochwat et al.


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Short summary
On the Antarctic Peninsula, there is a small bay that had sea ice fastened to the shoreline ('fast ice') for over a decade. The fast ice stabilized the glaciers that fed into the ocean. In January 2022 this fast ice broke away, using satellite data we found that this was because of low sea ice concentrations and a high long period ocean wave swell. We find that the glaciers have responded to this event by thinning, speeding up, and retreating by breaking off lots of icebergs at remarkable rates.