Physical and ecological processes at a moving ice edge in the Fram Strait as observed with an AUV

Abstract

a b s t r a c tSmall-scale investigations of physical and biogeochemical parameters have been carried out with an autonomous underwater vehicle (AUV) at a moving ice edge in the Fram Strait. The AUV was equipped with various sensors to study the complex interactions between physical and ecological processes along the ice edge and the associated meltwater front. The AUV covered two cross-front sections of 9 km and recorded high resolution vertical profiles of the physical and biogeochemical properties between 0 and 50 m water depth at a horizontal station spacing of 800-1000 m.In both physical and biogeochemical terms, the measurements revealed a complex structure of the water column. The distribution of phytoplankton biomass (chlorophyll a) and nutrients was highly inhomogeneous. Chlorophyll a concentrations of 5 mg l À 1 were detected at the frontal interface in a small corridor just 2-4 km wide and only 5 m deep. Nutrients at the surface were depleted, yet, compared to previous studies of this region, were still present in the euphotic zone. Below the euphotic zone, nitrate concentrations of 8 mmol l À 1 and oxygen saturation values of 100% resulted in a "dome-like" patternsuggestive of vertical transport processes. Based on these measurements, three different zones featuring individual biogeochemical characteristics were identified in the cross-front sections. Atmospheric forcing and the presence of the melt water front are assumed to be mainly responsible for the complexity of the water column. Localized vertical transport events seem to have occurred before our investigations. Furthermore, wind driven frontogenesis likely contributed to vertical water movements. All processes had an effect on the biological processes along the observed meltwater front.

Observations of a Submesoscale Cyclonic Filament in the Marginal Ice Zone

“…Patch formation (Prairie et al, ) is still an unsolved but important problem in marine biology. Fronts are known to relate to patches of phytoplankton (Wulff et al, ), zooplankton (Trudnowska et al, ), and marine birds and mammals (Joiris & Falck, ) in Fram Strait. The CTD casts suggest that the submesoscale filament may have a similar structuring ability on biomass and nutrient distributions as well as biological communities.…”

Hourly In Situ Nitrate on a Coastal Mooring: A 15-Year Record and Insights into New Production

“…In the future, increasing data collection spatial resolution through deployments on other autonomous platforms such as surface wave gliders, autonomous underwater vehicles, and autonomous profiling floats will serve to further expand potential research capabilities. Both ISUS (Johnson and Needoba, 2008;Ryan et al, 2010;Harvey et al, 2012;Zhang et al, 2015;Fischer et al, 2017) and SUNA (Wulff, 2016;Karstensen et al, 2017) nitrate sensors have been successfully deployed on autonomous underwater vehicles. In the future, incorporation of UV optical nitrate sensors along with pH and pCO 2 sensors on surface wave gliders (Chavez et al, 2017b) will provide quantitative data on the coupling of the carbon and nutrient cycles.…”

Assessing Phytoplankton Activities in the Seasonal Ice Zone of the Greenland Sea Over an Annual Cycle

“…The miniaturization of biogeochemical sensors allow their implementation on autonomous underwater vehicles (AUVs, e.g., ice-tethered profilers, gliders and Argo floats). Successful deployments of AUVs in the pan-Arctic area provide new physical and biogeochemical insights, even in the presence of sea ice (e.g., Laney et al, 2014;Wulff et al, 2016). Nowadays, BGC-Argo floats are largely used to evaluate the NCP in different ocean basins (e.g., Bushinsky & Emerson, 2015;Hennon et al, 2016;Plant et al, 2016;Riser et al, 2018;Yang et al, 2017).…”