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Influence of ice thickness and surface properties on light transmission through A rctic sea ice

View Article: PubMed Central - PubMed

ABSTRACT

The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea‐ice‐melt and under‐ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under‐ice radiance and irradiance using the new Nereid Under‐Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H‐ROV) designed for both remotely piloted and autonomous surveys underneath land‐fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under‐ice optical measurements with three dimensional under‐ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice‐thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under‐ice light field on small scales (<1000 m2), while sea ice‐thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

No MeSH data available.


(a) Map showing the cruise track (red line) in the northern Fram Strait between Greenland and Spitsbergen. The black x indicates the location of the presented ice station work. Sea ice concentration of the sampling day from AMSR2 (http://www.iup.uni‐bremen.de:8084/amsr2/) is shown in grey shadings with high sea ice concentration in brighter colors. (b) NUI shortly before deployment into a pool of open water on the starboard side of Polarstern. The upward looking sensors are located in the spine payload bay in between the two white landing skids toward the front of the vehicle.
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jgrc21358-fig-0001: (a) Map showing the cruise track (red line) in the northern Fram Strait between Greenland and Spitsbergen. The black x indicates the location of the presented ice station work. Sea ice concentration of the sampling day from AMSR2 (http://www.iup.uni‐bremen.de:8084/amsr2/) is shown in grey shadings with high sea ice concentration in brighter colors. (b) NUI shortly before deployment into a pool of open water on the starboard side of Polarstern. The upward looking sensors are located in the spine payload bay in between the two white landing skids toward the front of the vehicle.

Mentions: Measurements were carried out during the expedition of the German research ice‐breaker RV Polarstern to the Aurora mount, a hydrothermal vent site at Gakkel Ridge off Northeast Greenland (Figure 1a) [Boetius, 2015]. The described sea ice floe was surveyed on station PS86/080 at 82° 51′ N and 6° 19′ W on 28 July 2014 by on‐site ice‐thickness drillings combined with an under‐ice survey of NUI and aerial images taken during a helicopter survey. Snow thickness was measured using a MagnaProbe (Snow Hydro, Fairbanks, AK, USA). During the study, air temperature was slightly below 0°C, the average sea ice drift velocity was 0.3 kn, and ice concentration was 80%.


Influence of ice thickness and surface properties on light transmission through A rctic sea ice
(a) Map showing the cruise track (red line) in the northern Fram Strait between Greenland and Spitsbergen. The black x indicates the location of the presented ice station work. Sea ice concentration of the sampling day from AMSR2 (http://www.iup.uni‐bremen.de:8084/amsr2/) is shown in grey shadings with high sea ice concentration in brighter colors. (b) NUI shortly before deployment into a pool of open water on the starboard side of Polarstern. The upward looking sensors are located in the spine payload bay in between the two white landing skids toward the front of the vehicle.
© Copyright Policy - creativeCommonsBy-nc-nd
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016760&req=5

jgrc21358-fig-0001: (a) Map showing the cruise track (red line) in the northern Fram Strait between Greenland and Spitsbergen. The black x indicates the location of the presented ice station work. Sea ice concentration of the sampling day from AMSR2 (http://www.iup.uni‐bremen.de:8084/amsr2/) is shown in grey shadings with high sea ice concentration in brighter colors. (b) NUI shortly before deployment into a pool of open water on the starboard side of Polarstern. The upward looking sensors are located in the spine payload bay in between the two white landing skids toward the front of the vehicle.
Mentions: Measurements were carried out during the expedition of the German research ice‐breaker RV Polarstern to the Aurora mount, a hydrothermal vent site at Gakkel Ridge off Northeast Greenland (Figure 1a) [Boetius, 2015]. The described sea ice floe was surveyed on station PS86/080 at 82° 51′ N and 6° 19′ W on 28 July 2014 by on‐site ice‐thickness drillings combined with an under‐ice survey of NUI and aerial images taken during a helicopter survey. Snow thickness was measured using a MagnaProbe (Snow Hydro, Fairbanks, AK, USA). During the study, air temperature was slightly below 0°C, the average sea ice drift velocity was 0.3 kn, and ice concentration was 80%.

View Article: PubMed Central - PubMed

ABSTRACT

The observed changes in physical properties of sea ice such as decreased thickness and increased melt pond cover severely impact the energy budget of Arctic sea ice. Increased light transmission leads to increased deposition of solar energy in the upper ocean and thus plays a crucial role for amount and timing of sea‐ice‐melt and under‐ice primary production. Recent developments in underwater technology provide new opportunities to study light transmission below the largely inaccessible underside of sea ice. We measured spectral under‐ice radiance and irradiance using the new Nereid Under‐Ice (NUI) underwater robotic vehicle, during a cruise of the R/V Polarstern to 83°N 6°W in the Arctic Ocean in July 2014. NUI is a next generation hybrid remotely operated vehicle (H‐ROV) designed for both remotely piloted and autonomous surveys underneath land‐fast and moving sea ice. Here we present results from one of the first comprehensive scientific dives of NUI employing its interdisciplinary sensor suite. We combine under‐ice optical measurements with three dimensional under‐ice topography (multibeam sonar) and aerial images of the surface conditions. We investigate the influence of spatially varying ice‐thickness and surface properties on the spatial variability of light transmittance during summer. Our results show that surface properties such as melt ponds dominate the spatial distribution of the under‐ice light field on small scales (<1000 m2), while sea ice‐thickness is the most important predictor for light transmission on larger scales. In addition, we propose the use of an algorithm to obtain histograms of light transmission from distributions of sea ice thickness and surface albedo.

No MeSH data available.