Articles | Volume 11, issue 3
The Cryosphere, 11, 1141–1148, 2017
The Cryosphere, 11, 1141–1148, 2017

Research article 08 May 2017

Research article | 08 May 2017

Could promontories have restricted sea-glacier penetration into marine embayments during Snowball Earth events?

Adam J. Campbell1,a, Betzalel Massarano1,b, Edwin D. Waddington1, and Stephen G. Warren1,2 Adam J. Campbell et al.
  • 1Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
  • 2Astrobiology Program, University of Washington, Seattle, Washington, USA
  • anow at: School of Surveying, University of Otago, Dunedin, New Zealand
  • bnow at: Pacific Science Center, Seattle, Washington, USA

Abstract. During the Neoproterozoic (∼  1000–550 Ma), Earth experienced several climate excursions of extreme cold, often referred to as the Snowball Earth events. During these periods, thick flowing ice, referred to as sea glaciers, covered the entire planet's oceans. In addition, there is evidence that photosynthetic eukaryotic algae survived during these periods. With thick sea glaciers covering the oceans, it is uncertain where these organisms survived. One hypothesis is that these algae survived in marine embayments hydrologically connected to the global ocean, where the flow of sea glacier could be resisted. In order for an embayment to act as a refugium, the invading sea glacier must not completely penetrate the embayment. Recent studies have shown that straight-sided marine embayments could have prevented full sea-glacier penetration under a narrow range of climate conditions suitable for the Snowball Earth events. Here we test whether promontories, i.e., headlands emerging from a side shoreline, could further restrict sea-glacier flow. We use an ice-flow model, suitable for floating ice, to determine the flow of an invading sea glacier. We show that promontories can expand the range of climate conditions allowing refugia by resisting the flow of invading sea glaciers.

Short summary
How could plant life, that needs light to survive, live on a planet covered with ice? Such a situation is thought to have existed during what are called the Snowball Earth events over 600 million years ago. Here we find that ice shadows, regions where ice has difficulty flowing into, may have a played a role in that survival of early plant life.