NABOS Technology

We have deployed several moorings shaped in a cross-isobath section at 125°E. Six moorings were deployed in 2013 at this cross-section, covering the depth range from 300m to 4000m.

Climatology shows that the Atlantic Water (AW) core defined by the temperature maximum is located over the 2500-3000m isobaths along the Laptev Sea slope. Seven NABOS CTD cross-sections (i.e. 2002, 2004-09) captured the core within this range.

The only exception was in 2003 when there were two AW cores; the deeper one was shifted to the north, and was not resolved by the section. However, the northern station of this section was located over the ~3500-m isobath. Thus, the mooring section will capture the major AW transports. The McLane Moored Profiler (MMP) climbs up and down along a mooring line providing high-resolution T, S, and velocity profiles.

We are using MMPs within the ~50-750m (i.e. AW+halocline) depth range with one profile per three days, thus obtaining a good climatological record and preserving MMP battery power (which was a problem in the past). The shallowest and central moorings will use conventional equipment.

Data from these moorings will be used to define the spatial structure of the boundary current, for estimating along-slope transports and cross-slope AW core displacements.

Satlantic V2 ISUS nitrate sensors have been added to moorings and deployed alongside Seabird CTDs; additional dissolved oxygen measuring capabilities in lower halocline waters provide year-round monitoring of the quasi-conservative tracer NO. Alkire et al. [2010] found variability in vertical profiles of NO to be highly complex and illuminating in the study of halocline ventilation and its variability. Such detail cannot be captured without sensor-based measurements.

Lagrangian buoys will be deployed in the eastern EMB, providing the longest drift trajectories through the eastern Arctic Ocean. These buoy observations are an essential part of AON and this project.

Ice-Tethered Profilers

ITPs are provided by WHOI and will be deployed during each cruise. We plan to deploy the instruments on ice. During the NABOS cruise in 2009, two ITPs were deployed for the first time in open water; they incorporated a new-style surface package designed to be more robust in Marginal Ice Zone conditions. Thus, ice conditions will not preclude ITP deployments. The ITP profilers operate on typical sampling schedules of two one-way CTD profiles between 7 and 760 m depth each day.

Building on the ongoing success of ice drifters that support multiple discrete subsurface sensors on tethers and the WHOI-developed Moored Profiler instrument capable of moving along a tether to sample at better than 1-m vertical resolution, WHOI researchers designed and field tested an automated, easily-deployed ITP for Arctic study.

The system consists of a small surface capsule housing a controller interfaced to an Iridium data telemetry unit and inductive modem, a plastic-jacketed wire rope tether extending down 500 to 800 m into the ocean terminated by a ballast weight, and a new variation of the WHOI Moored Profiler (in shape and size much like an Argo float) that mounts on the tether and cycles vertically along it. Communication between the Profiler and surface controller is supported by an inductive modem (utilizing the wire tether and seawater return), and between the surface unit and shore via a satellite link.

Data from the ITPs are broadcast within hours of acquisition and made available on the ITP website.

Ice Mass Buoys

The IMB is an autonomous, ice-based system, designed to measure and attribute thermodynamic changes in the mass balance of the sea ice cover.

The instrumentation of the autonomous mass balance buoys typically consists of a Campbell scientific datalogger, an Argos transmitter, a thermistor string, and above ice and below ice acoustic sounders measuring the positions of the surface and bottom within 5 mm.

In addition to the mass balance instrumentation the buoys also have a GPS, a barometer, and an air temperature sensor. Thermistor strings were PVC rod with YSI thermistors spaced every 10 cm. These rods could easily be connected to assemble strings that extended from the air through the snow and ice into the upper ocean. The thermistor accuracy is better than 0.1°C.

Meteorological Buoys SVP (Surface Velocity Profiler)

Several meteorological buoys (IABPs) provided by APL (I. Rigor), and Meteo France (Pierre Blouch) are available for deployment during each cruise.

The SVP are buoys that have been used for the World Ocean Circulation Experiment (WOCE) buoys for many years, and given the increasing amounts of open water in the Arctic, the IABP has been using these buoys on sea ice and in the open water with very good success.

The basic SVP measure ocean currents (or ice motion) and sea surface temperature, but we have been deploying SVP buoys that have been upgraded with a barometer (SVP-B).

Some of these buoys have also been upgraded to include a GPS which is more accurate (better than 5 m) than the Argos positioning (typically +/- 120 m). The basic SVP typically reports for 18 months in the wet ocean, but depending on the deployment conditions, these buoys typically report for about 9-12 months. As always, one of the trade offs for additional instruments (barometer, GPS) is a shorter battery life.

Most buoys report via Argos, but many have started using Iridium (e.g. the ITP, and possibly the IMB this year).

O-Buoys

The focus of this work is on understanding the behavior of O3 and CO2, as two of the most important greenhouse gases that are as yet poorly understood.

The buoy also measures bromine oxide (BrO), a key species responsible for the extraordinary polar springtime O3 and Hg atmospheric depletion , both of which have strong consequences for human and ecosystem health in the Arctic region.

There are a variety of potential connections between these three species. O3 is a critical and central molecule in the troposphere. It indirectly but profoundly affects the abundance of most trace gases, including many greenhouse gases. Lower atmosphere depletions in O3 seen in the Arctic during springtime are highly correlated to deposition of Hg, a toxic and bio-accumulative pollutant; thus it also indicates and possibly determines Hg behavior.

This coupled Hg and O3 chemistry is driven by bromine radicals (Br and BrO). Therefore, observations of BrO directly quantify a key catalyst in Arctic atmospheric chemistry and provide a link to the cycling of O3 and Hg in this region. A long standing hypothesis is that both micro and macro-algae emit organo-halogen species that may be initiators of the halogen chemistry that destroys O3, producing the intermediate BrO.

The fluxes of organo-halogen compounds are tied to primary productivity and thus to some extent to CO2 fluxes. Fluxes of halogen precursors and CO2 may or may not be tied to the presence of open leads. CO2 is exchanged by biological processes and thus is an indicator of biological activity, coupled to the physical characteristics of the open ocean and sea ice surfaces.

While CO2 is readily exchanged between the atmosphere and the sea water, the role of sea ice as a barrier to, or integral player in, this process is only poorly understood. In spite of their importance, very little data exists on O3, BrO and CO2 concentrations in the Arctic Ocean region, and very little indeed over the Arctic Ocean surface. However, the scarce data for these key atmospheric species in the Arctic Ocean region itself is primarily due to the lack of capability.