Response of biological productivity to North Atlantic marine front migration during the Holocene

Abstract

Abstract. Marine fronts delineate the boundary between distinct water masses and, through the advection of nutrients, are important facilitators of regional productivity and biodiversity. As the modern climate continues to change, the migration of frontal zones is evident, but a lack of information about their status prior to instrumental records hinders future projections. Here, we combine data from lipid biomarkers (archaeal isoprenoid glycerol dibiphytanyl glycerol tetraethers and algal highly branched isoprenoids) with planktic and benthic foraminifera assemblages to detail the biological response of the marine Arctic and polar front migrations on the North Iceland Shelf (NIS) over the last 8 kyr. This multi-proxy approach enables us to quantify the thermal structure relating to Arctic and polar front migration and test how this influences the corresponding changes in local pelagic productivity. Our data show that following an interval of Atlantic water influence, the Arctic front and its associated high pelagic productivity migrated southeastward to the NIS by ∼6.1 ka. Following a subsequent trend in regional cooling, Polar Water from the East Greenland Current and the associated polar front spread onto the NIS by ∼3.8 ka, greatly diminishing local algal productivity through the Little Ice Age. Within the last century, the Arctic and polar fronts have moved northward back to their current positions relative to the NIS and helped stimulate the productivity that partially supports Iceland's economy. Our Holocene records from the NIS provide analogues for how the current frontal configuration and the productivity that it supports may change as global temperatures continue to rise.

Biomarker characterization of the North Water Polynya, Baffin Bay: implications for local sea ice and temperature proxies

“…3.2) can also be used as the phytoplankton biomarker in lieu of HBI III (e.g., Müller et al, 2011). Although in some regions high concentrations of HBI III have also been associated with highly productive marginal ice zones (Barents Sea, Belt et al, 2019), marine fronts (North Iceland Shelf, Harning et al, 2021), and sea ice (Amiraux et al, 2019(Amiraux et al, , 2021Koch et al, 2020) that may complicate PIP 25 -derived indices, recent compilations of Arctic surface sediments show that PIP 25 -based indices broadly correlate with spring and autumn sea ice concentrations (Xiao et al, 2015;Kolling et al, 2020).…”

Efficiency of sympagic-benthic coupling revealed by analyses of n-3 fatty acids, IP25 and other highly branched isoprenoids in two filter-feeding Arctic benthic molluscs: Mya truncata and Serripes groenlandicus

“…1), has shown potential as a proxy of pelagic production for the spring marginal ice zone (MIZ) in polar seas (Belt et al, 2019;Collins et al, 2013;Köseoğlu et al, 2018;Smik et al, 2016a;Smik et al, 2016b). More recently, HBI III has also shown potential as a proxy for pelagic productivity associated with arctic sea fronts (Harning et al, 2020).…”

Destabilisation of the Subpolar North Atlantic prior to the Little Ice Age

“…4a). The presence of sea ice likely disrupted primary production and food supply to the sea bed 34 , as the observed decline in shell growth around 1300 suggests (Fig. 2c).…”