The aim of the ANDRILL McMurdo Ice Shelf (MIS) Project was to obtain a continuous sediment core through approximately c. 1 200 metres (m) of Neogene ( c. 0 to 10 Ma) glacimarine, terrigenous, volcanic, and biogenic sediment that has accumulated in the Windless Bight region under the McMurdo Ice Shelf. The present-day MIS forms the northwest part of Ross Ice Shelf where it has been pinned by Ross Island for the last c. 10 k.y. and is nourished by ice sourced from East Antarctic Ice Sheet (EAIS) outlet glaciers in the southern Transantarctic Mountains (TAM). The MIS drill site was situated c. 10 kilometres (km) east of Hut Point Peninsula (77.8894417°-S, 167.0893282°-E) above a flexural moat basin formed in response to Quaternary volcanic loading of the crust by Ross Island, superimposed on more regional subsidence associated with Neogene extension of the Terror Rift. The significant results thus far are that the Ross Ice Sheet has undergone significant cyclic variations in extent and timing during the Late Neogene. A relatively colder and more persistent ice sheet dominated the Ross Embayment in the early Late Miocene between 13 and 10 Ma, becoming more dynamic in the Late Miocene ( c. 9 to 7 Ma), with significant water discharge via subglacial conduits in the latest Miocene-Early Pliocene (5 to 2.5 Ma). This period also saw times when the Ross Embayment was relatively ice-free, with highly productive, warmer oceanic conditions ( e.g. at c. 4 Ma and 1.1 Ma). From Middle Pleistocene to Recent, the ice sheet is characterised by a change back to more stable, colder ice sheet conditions. Our preliminary analysis of the more than 25 Pliocene sedimentary cycles indicates significant glacial-interglacial variability, with regular oscillations between subglacial/ice proximal and open ocean ice distal environments, including extended periods of interglacial warmth when the ice was not calving into the ocean. Our environmental reconstructions to date imply changes in ice-sheet volume that must have contributed significantly to eustasy and ocean circulation.
Background to the ANDRILL McMurdo Ice Shelf Project (Antarctica) and Initial Science Volume
2007
Abstract
The aim of the ANDRILL McMurdo Ice Shelf (MIS) Project was to obtain a continuous sediment core through approximately c. 1 200 metres (m) of Neogene ( c. 0 to 10 Ma) glacimarine, terrigenous, volcanic, and biogenic sediment that has accumulated in the Windless Bight region under the McMurdo Ice Shelf. The present-day MIS forms the northwest part of Ross Ice Shelf where it has been pinned by Ross Island for the last c. 10 k.y. and is nourished by ice sourced from East Antarctic Ice Sheet (EAIS) outlet glaciers in the southern Transantarctic Mountains (TAM). The MIS drill site was situated c. 10 kilometres (km) east of Hut Point Peninsula (77.8894417°-S, 167.0893282°-E) above a flexural moat basin formed in response to Quaternary volcanic loading of the crust by Ross Island, superimposed on more regional subsidence associated with Neogene extension of the Terror Rift. The significant results thus far are that the Ross Ice Sheet has undergone significant cyclic variations in extent and timing during the Late Neogene. A relatively colder and more persistent ice sheet dominated the Ross Embayment in the early Late Miocene between 13 and 10 Ma, becoming more dynamic in the Late Miocene ( c. 9 to 7 Ma), with significant water discharge via subglacial conduits in the latest Miocene-Early Pliocene (5 to 2.5 Ma). This period also saw times when the Ross Embayment was relatively ice-free, with highly productive, warmer oceanic conditions ( e.g. at c. 4 Ma and 1.1 Ma). From Middle Pleistocene to Recent, the ice sheet is characterised by a change back to more stable, colder ice sheet conditions. Our preliminary analysis of the more than 25 Pliocene sedimentary cycles indicates significant glacial-interglacial variability, with regular oscillations between subglacial/ice proximal and open ocean ice distal environments, including extended periods of interglacial warmth when the ice was not calving into the ocean. Our environmental reconstructions to date imply changes in ice-sheet volume that must have contributed significantly to eustasy and ocean circulation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
