Modern foraminiferal assemblages in northern Nares Strait, Petermann Fjord, and beneath Petermann ice tongue, NW Greenland

Anne Jennings,John Andrews,Brendan Reilly,Maureen Walczak,Martin Jakobsson,Alan Mix,Joe Stoner,Keith W Nicholls,Maziet Cheseby

doi:10.1080/15230430.2020.1806986

Abstract

ABSTRACT Calving events of Petermann Glacier, northwest Greenland, in 2010 and 2012 reduced the length of its ice tongue by c. 25 km, allowing exploration of newly uncovered seafloor during the Petermann 2015 Expedition. This article presents the results of foraminiferal analysis and environmental data from thirteen surface sediment samples in northern Nares Strait and Petermann Fjord, including beneath the modern ice tongue. This is the first study of living foraminifera beneath an arctic ice tongue and the first modern foraminiferal data from this area. Modern assemblages were studied to constrain species environmental preferences and to improve paleoenvironmental interpretations of foraminiferal assemblages. Sub–ice tongue assemblages differed greatly from those at all other sites, with very low faunal abundances and being dominated by agglutinated fauna, likely reflecting low food supply under the ice tongue. Fjord fauna were comprised of 80 percent or more calcareous species. Notably, Elphidium clavatum is absent beneath the ice tongue although it is dominant in the fjord. Increasing primary productivity associated with the transition to mobile sea ice, diminishing influence of the Petermann Glacier meltwater with distance from the grounding line, and increased influence of south-flowing currents in Nares Strait are the important controls on the faunal assemblages.

Highlights

Foraminiferal biostratigraphies in sediment archives are important for interpreting arctic paleoceanography and paleoclimate (e.g., Jennings et al 2011; Perner et al 2012; Polyak et al 2013; Seidenkrantz 2013)
Several modern assemblage studies using various size fractions have been reported from the Arctic Ocean (e.g., Lagoe 1977; Bergsten 1994; Wollenburg and Mackensen 1998; Osterman, Poore, and Foley 1999; Wollenburg and Kuhnt 2000) and the adjacent shelf areas (e.g., Schröder-Adams et al 1990; Jennings and Helgadottir 1994; Scott et al 2008), and these studies have demonstrated that arctic benthic foraminifera respond to fluxes of labile and refractory organic matter to the seabed, sedimentation rates, water mass varia tions, salinity, temperature, turbidity, and water column stratification, all of which are related to sea-ice cover, the presence of marine or terrestrial terminating glaciers, and the advection of Atlantic and polar water, making foraminiferal assemblages valuable for arctic paleoenvir onmental reconstructions
Rapid climate and environmental changes already underway in the Arctic underscore the urgency of gath ering modern foraminiferal assemblage data, both to provide modern analogues for past conditions recorded in sediment cores and to provide a baseline to evaluate the faunal responses to rapidly changing arctic cryo sphere and ocean conditions

Summary

Introduction

Foraminiferal biostratigraphies in sediment archives are important for interpreting arctic paleoceanography and paleoclimate (e.g., Jennings et al 2011; Perner et al 2012; Polyak et al 2013; Seidenkrantz 2013). Modern arctic foraminiferal assemblages provide the most secure basis for interpreting past environmental change from fossil assemblages and for establishing the environmen tal preferences of key species used in paleoenvironmen tal interpretations. Such modern studies are rare in the Arctic, partly because they rely on collection of surface sediments from remote sites that are difficult to access. The Petermann Glacier Expedition of Swedish icebreaker Oden in 2015

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