Glider App for public dissemination and outreach

D3.6 Glider App for public dissemination and outreach: Primarily developed for outreach purposes the application will also include some functionality for glider pilots. The App will interface in realtime with glider communication stations on land. Functionality will be based and tested on planned glider missions by SAMS partner and will then be rolled out to other partners

New insights into radiative transfer within sea ice derived from autonomous optical propagation measurements

The radiative transfer of shortwave solar radiation through the sea ice cover of the polar oceans is a crucial aspect of energy partitioning at the atmosphere–ice–ocean interface. A detailed understanding of how sunlight is reflected and transmitted by the sea ice cover is needed for an accurate representation of critical processes in climate and ecosystem models, such as the ice–albedo feedback. Due to the challenges associated with ice internal measurements, most information about radiative transfer in sea ice has been gained by optical measurements above and below the sea ice. To improve our understanding of radiative transfer processes within the ice itself, we developed a new kind of instrument equipped with a number of multispectral light sensors that can be frozen into the ice. A first prototype consisting of a 2.3 m long chain of 48 sideward planar irradiance sensors with a vertical spacing of 0.05 m was deployed at the geographic North Pole in late August 2018, providing autonomous, vertically resolved light measurements within the ice cover during the autumn season. Here we present the first results of this instrument, discuss the advantages and application of the prototype, and provide first new insights into the spatiotemporal aspect of radiative transfer within the sea ice itself. In particular, we investigate how measured attenuation coefficients relate to the optical properties of the ice pack and show that sideward planar irradiance measurements are equivalent to measurements of total scalar irradiance

Robust wavebuoys for the marginal ice zone: Experiences from a large persistent array in the Beaufort Sea

An array of novel directional wavebuoys was designed and deployed into the Beaufort Sea ice cover in March 2014, as part of the Office of Naval Research Marginal Ice Zone experiment. The buoys were designed to drift with the ice throughout the year and monitor the expected breakup and retreat of the ice cover, forced by waves travelling into the ice from open water. Buoys were deployed from fast-and-light air-supported ice camps, based out of Sachs Harbour on Canada’s Banks Island, and drifted westwards with the sea ice over the course of spring, summer and autumn, as the ice melted, broke up and finally re-froze. The buoys transmitted heave, roll and pitch timeseries at 1 Hz sample frequency over the course of up to eight months, surviving both convergent ice dynamics and significant waves-in-ice events. Twelve of the 19 buoys survived until their batteries were finally exhausted during freeze-up in late October/November. Ice impact was found to have contaminated a significant proportion of the Kalman-filter-derived heave records, and these bad records were removed with reference to raw x/y/z accelerations. The quality of magnetometer-derived buoy headings at the very high magnetic field inclinations close to the magnetic pole was found to be generally acceptable, except in the case of four buoys which had probably suffered rough handling during transport to the ice. In general, these new buoys performed as expected, though vigilance as to the veracity of the output is required

Sea-ice decline could keep zooplankton deeper for longer

As Arctic sea ice deteriorates, more light enters the ocean, causing largely unknown effects on the ecosystem. Using an autonomous biophysical observatory, we recorded zooplankton vertical distribution under Arctic sea ice from dusk to dawn of the polar night. Here we show that zooplankton ascend into the under-ice habitat during autumn twilight, following an isolume of 2.4 × 10−4 W m−2. We applied this trigger isolume to CMIP6 model outputs accounting for incoming radiation after sunset and before sunrise of the polar night. The models project that, in about three decades, the total time spent by zooplankton in the under-ice habitat could be reduced by up to one month, depending on geographic region. This will impact zooplankton winter survival, the Arctic foodweb, and carbon and nutrient fluxes. These findings highlight the importance of biological processes during the twilight periods for predicting change in high-latitude ecosystems

New tools for optical measurements in sea ice

The quantity and quality of sunlight transmitted into and through sea ice is a crucial key necessary to understand the thermodynamic development of the ice cover, upper ocean heat and freshwater budget, as well as the associated primary production. Due to its solid impenetrable nature, most optical measurements so far have been conducted above and underneath the sea ice covering our polar oceans. Only very limited measurements have been carried out inside the ice cover itself. This strongly limits our current knowledge of the vertically varying inherent optical properties (IOP) of sea ice, as well as the geometric shape of the in-ice light field. Both factors currently limit our abilities to reliably model radiative transfer in sea ice. Here we present multiple new tools that can fill this observational gap and provide comprehensive optical measurements within the ice: This includes a chain of multispectral light sensors for seasonal long-term monitoring. It is derived from the proven design of the newest generation of ice-mass-balance buoys with digital thermistor strings and enables a non-destructive measurement with flexible geometry. We present data from a first prototype deployed together with an array of drifting ice observatories at the North Pole in September 2018. These vertically resolved in-ice light profiles are compared to in-ice measurements with a newly designed in-ice optical profiler system based on the well-proven TriOS Ramses hyperspectral radiometers. Combining expertise from photonics, medical and sea-ice science enables the ongoing development of a set of endoscopic probes allowing optical studies in sea ice with minimum disturbance of the ice. This includes in-ice microscopy for in-situ ice algal investigations, a UV-spectrometer to observe brine nitrate concentration in situ, a reflectance probe for high-resolution direct determination of inherent optical properties, as well as a radiance camera for quantification of the angular radiance distribution. Here we present data from the first field tests during the Arctic field season 2018. First ruggedized prototypes could be available to the scientific community soon

Under-Ice Light Field in the Western Arctic Ocean During Late Summer

The Arctic is no longer a region dominated by thick multi-year ice (MYI), but by thinner, more dynamic, first-year-ice (FYI). This shift towards a seasonal ice cover has consequences for the under-ice light field, as sea-ice and its snow cover are a major factor influencing radiative transfer and thus, biological activity within- and under the ice. This work describes in situ measurements of light transmission through different types of sea-ice (MYI and FYI) performed during two expeditions to the Chukchi sea in August 2018 and 2019, as well as a simple characterisation of the biological state of the ice microbial system. Our analysis shows that, in late summer, two different states of FYI exist in this region: 1) FYI in an enhanced state of decay, and 2) robust FYI, more likely to survive the melt season. The two FYI types have different average ice thicknesses: 0.74 ± 0.07 m (N = 9) and 0.93 ± 0.11 m (N = 9), different average values of transmittance: 0.15 ± 0.04 compared to 0.09 ± 0.02, and different ice extinction coefficients: 1.49 ± 0.28 and 1.12 ± 0.19 m−1. The measurements performed over MYI present different characteristics with a higher average ice thickness of 1.56 ± 0.12 m, lower transmittance (0.05 ± 0.01) with ice extinction coefficients of 1.24 ± 0.26 m−1 (N = 12). All ice types show consistently low salinity, chlorophyll a concentrations and nutrients, which may be linked to the timing of the measurements and the flushing of melt-water through the ice. With continued Arctic warming, the summer ice will continue to retreat, and the decayed variant of FYI, with a higher scattering of light, but a reduced thickness, leading to an overall higher light transmittance, may become a more relevant ice type. Our results suggest that in this scenario, more light would reach the ice interior and the upper-ocean