The morphology of pockmarks on the north-east Antarctic Peninsula continental shelf

Abstract

Pockmarks are sea-floor depressions that form when gas or liquid escapes from underlying sediments. Although they are a common feature of both glaciated and lower-latitude continental shelves, pockmarks have not been reported previously from the north-east Antarctic Peninsula margin. Here we use high-resolution geophysical data acquired using autonomous underwater vehicles to map > 240 pockmarks in three locations along the north-east Antarctic Peninsula shelf. The pockmarks are 0.4–45 m wide and 0.1–2.5 m deep, encompassing both smaller unit-pockmarks and larger normal-pockmarks. The high resolution of our data enables the identification of subdued features associated with the pockmarks, including acoustic flares within the water column, ejecta rims, intra-pockmark blocks and possibly even biological structures. The overprinting of subglacial and ice-marginal landforms by the pockmarks constrains their timing of formation to the last ~11 ka. The high density of pockmarks within the surveyed areas, together with geophysical evidence for the active seepage of gas to the sea floor, suggests that the expulsion of subsurface fluids is a widespread process on the north-east Antarctic Peninsula shelf that could have important implications for benthic biodiversity and the global carbon cycle.

Antarctic Seabed Assemblages in an Ice-Shelf-Adjacent Polynya, Western Weddell Sea

“…Benthic megafaunal assemblages were investigated at four sites, LCP1-4 ( Table 1 ), situated at various distances from the nearest ice-shelf front, i.e., coastline (ranging from <1 to ~16 km, and labeled accordingly, with LCP1 being closest to the ice shelf and LCP4 farthest away). The sites were located on either side of the glacially-deepened Jason Trough [ 76 , 77 , 78 ]. LCP1 was the most southerly site, close to Bawden Ice Rise, and LCP2-4 were located north of Jason Trough, near Cape Framnes at the tip of Jason Peninsula.…”