Estimating Underwater Light Regime under Spatially Heterogeneous Sea Ice in the Arctic

The vertical diffuse attenuation coefficient for downward plane irradiance ( K d ) is an apparent optical property commonly used in primary production models to propagate incident solar radiation in the water column. In open water, estimating K d is relatively straightforward when a vertical profile of measurements of downward irradiance, E d , is available. In the Arctic, the ice pack is characterized by a complex mosaic composed of sea ice with snow, ridges, melt ponds, and leads. Due to the resulting spatially heterogeneous light field in the top meters of the water column, it is difficult to measure at single-point locations meaningful K d values that allow predicting average irradiance at any depth. The main objective of this work is to propose a new method to estimate average irradiance over large spatially heterogeneous area as it would be seen by drifting phytoplankton. Using both in situ data and 3D Monte Carlo numerical simulations of radiative transfer, we show that (1) the large-area average vertical profile of downward irradiance, E d ¯ ( z ) , under heterogeneous sea ice cover can be represented by a single-term exponential function and (2) the vertical attenuation coefficient for upward radiance ( K L u ), which is up to two times less influenced by a heterogeneous incident light field than K d in the vicinity of a melt pond, can be used as a proxy to estimate E d ¯ ( z ) in the water column.

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Distribution of 210Pb and 210Po in the Arctic water column during the 2007 sea-ice minimum: Particle export in the ice-covered basins

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/j.dsr.2018.09.011 ◽

2018 ◽

Vol 142 ◽

pp. 94-106 ◽

Cited By ~ 3

Author(s):

Montserrat Roca-Martí ◽

Viena Puigcorbé ◽

Jana Friedrich ◽

Michiel Rutgers van der Loeff ◽

Benjamin Rabe ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

The Arctic ◽

Arctic Water ◽

Particle Export

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Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic

Biogeosciences ◽

10.5194/bg-14-3129-2017 ◽

2017 ◽

Vol 14 (12) ◽

pp. 3129-3155 ◽

Cited By ~ 17

Author(s):

Hakase Hayashida ◽

Nadja Steiner ◽

Adam Monahan ◽

Virginie Galindo ◽

Martine Lizotte ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Dimethyl Sulfide ◽

Phytoplankton Bloom ◽

Model Simulation ◽

Field Measurements ◽

Sulfur Cycle ◽

The Arctic ◽

Model Parameters ◽

Ocean Ecosystem

Abstract. Sea ice represents an additional oceanic source of the climatically active gas dimethyl sulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is, however, not known due to scarcity of field measurements. In this study, we developed a coupled sea ice–ocean ecosystem–sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emissions of DMS in the Arctic. The results of the 1-D model simulation were compared with field data collected during May and June of 2010 in Resolute Passage. Our results reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The release of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Production and removal rates of processes considered in the model are analyzed to identify the processes dominating the budgets of DMS and DMSP both in the bottom ice and the underlying water column. When openings in the ice were taken into account, the simulated sea–air DMS flux during the melt period was dominated by episodic spikes of up to 8.1 µmol m−2 d−1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that should be better constrained by new observations.

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Numerical investigation of the Arctic ice-ocean boundary layer; implications for air-sea gas fluxes

10.5194/os-2016-4 ◽

2016 ◽

Cited By ~ 1

Author(s):

A. Bigdeli ◽

B. Loose ◽

S. T. Cole

Keyword(s):

Sea Ice ◽

Water Column ◽

Mixed Layer ◽

Mixed Layer Depth ◽

The Arctic ◽

Layer Depth ◽

Near Surface ◽

Resolution Model ◽

Simplifying Assumptions ◽

Vertical Spacing

Abstract. In ice-covered regions it can be challenging to determine air-sea exchange – for heat and momentum, but also for gases like carbon dioxide and methane. The harsh environment and relative data scarcity make it difficult to characterize even the physical properties of the ocean surface. Here, we seek a mechanistic interpretation for the rate of air-sea gas exchange (k) derived from radon-deficits. These require an estimate of the water column history extending 30 days prior to sampling. We used coarse resolution (36 km) regional configuration of the MITgcm with fine near surface vertical spacing (2 m) to evaluate the capability of the model to reproduce conditions prior to sampling. The model is used to estimate sea-ice velocity, concentration and mixed-layer depth experienced by the water column. We then compared the model results to existing field data including satellite, moorings and Ice-tethered profilers. We found that model-derived sea-ice coverage is 88 to 98 % accurate averaged over Beaufort Gyre, sea-ice velocities have 78 % correlation which resulted in 2 km/day error in 30 day trajectory of sea-ice. The model demonstrated the capacity to capture the broad trends in the mixed layer although with a bias and model water velocities showed only 29 % correlation with actual data. Overall, we find the course resolution model to be an inadequate surrogate for sparse data, however the simulation results are a slight improvement over several of the simplifying assumptions that are often made when surface ocean geochemistry, including the use of a constant mixed layer depth and a velocity profile that is purely wind-driven.

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Sensitivity of the light field under sea ice to spatially inhomogeneous optical properties and incident light assessed with three-dimensional Monte Carlo radiative transfer simulations

Cold Regions Science and Technology ◽

10.1016/j.coldregions.2011.12.004 ◽

2012 ◽

Vol 73 ◽

pp. 1-11 ◽

Cited By ~ 16

Author(s):

Chris Petrich ◽

Marcel Nicolaus ◽

Rolf Gradinger

Keyword(s):

Monte Carlo ◽

Optical Properties ◽

Radiative Transfer ◽

Sea Ice ◽

Light Field ◽

Incident Light ◽

Three Dimensional ◽

Spatially Inhomogeneous

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Measurements on Air Porosity of Sea Ice

Annals of Glaciology ◽

10.1017/s0260305500005486 ◽

1983 ◽

Vol 4 ◽

pp. 204-208 ◽

Cited By ~ 12

Author(s):

Masayoshi Nakawo

Keyword(s):

Sea Ice ◽

Atmospheric Pressure ◽

Vertical Profile ◽

The Arctic ◽

First Year ◽

Saturation Ratio ◽

Air Content ◽

Bubble Pressure ◽

Density Values ◽

Good Agreement

The air content of sea ice can be measured directly by melting a sample and collecting the released air, provided the air saturation ratio in the meltwater is known. The saturation ratio was found experimentally to be a function of three parameters: the time after an ice sample was melted, the average bubble size, and the air porosity of the sample. Since the last parameter is the term to be determined, an iteration method was employed in calculations of porosity. The bubble pressure was assumed to be at one atmospheric pressure. The vertical profile of air porosity was thus obtained for first-year sea ice in the Arctic. The results were in good agreement with estimations of porosity made from density values measured for the same samples. This indicates that the bubble pressure is near one atmospheric pressure.

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How well does wind speed predict air-sea gas transfer in the sea ice zone? A synthesis of radon deficit profiles in the upper water column of the Arctic Ocean

Journal of Geophysical Research Oceans ◽

10.1002/2016jc012460 ◽

2017 ◽

Vol 122 (5) ◽

pp. 3696-3714 ◽

Cited By ~ 5

Author(s):

B. Loose ◽

R. P. Kelly ◽

A. Bigdeli ◽

W. Williams ◽

R. Krishfield ◽

...

Keyword(s):

Wind Speed ◽

Sea Ice ◽

Arctic Ocean ◽

Water Column ◽

The Arctic ◽

Gas Transfer ◽

The Arctic Ocean

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Wintertime Methane Emission From the Barents and Kara Seas and Sea of Okhotsk: Satellite Evidence.

10.5194/egusphere-egu21-5628 ◽

2021 ◽

Author(s):

Leonid Yurganov ◽

Dustin Carroll ◽

Andrey Pnyushkov ◽

Igor Polyakov ◽

Hong Zhang

Keyword(s):

Remote Sensing ◽

Sea Ice ◽

Water Column ◽

Mixed Layer Depth ◽

Deep Ocean ◽

Ice Cover ◽

The Arctic ◽

Atmospheric Methane ◽

Arctic Seas ◽

Ir Radiation

Existence of strong seabed sources of methane, including gas hydrates, in the Arctic and sub-Arctic seas with proven oil/gas deposits is well documented. Enhanced concentrations of dissolved methane in deep layers are widely observed. Many of marine sources are highly sensitive to climate change; however, the Arctic methane sea-to-air flux remains poorly understood: harsh natural conditions prevent in-situ measurements during winter. Satellite remote sensing, based on terrestrial outgoing Thermal IR radiation measurements, provides a novel alternative to those efforts. We present year-round methane data from 3 orbital sounders since 2002. Those data confirm that negligible amounts of methane are fluxed from the seabed to the atmosphere during summer. In summer, the water column is strongly stratified from sea-ice melt and solar warming. As a result, ~90% of dissolved methane is oxidized by bacteria. Conversely, some marine areas are characterized by positive atmospheric methane anomalies that begin in November. During winter, ocean stratification weakens, convection and winter storms mix the water column efficiently. We also find that the amplitudes of the seasonal cycles over Kara and Okhotsk Seas have increased during last 18 years due to winter concentration growth. There may be several factors responsible for sea-air flux: growing emission from clathrates due to warming, changes in methane transport from the seabed to the surface, changes in microbial oxidation, ice cover, etc. Finally, methane remote sensing results are compared to available observations of temperature in deep ocean layers, estimates of Mixed Layer Depth, and satellite microwave sea-ice cover measurements.&#160;

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Temporal evolution of IP25 and other highly branched isoprenoid lipids in sea ice and the underlying water column during an Arctic melting season

Elem Sci Anth ◽

10.1525/elementa.377 ◽

2019 ◽

Vol 7 ◽

Cited By ~ 4

Author(s):

Rémi Amiraux ◽

Lukas Smik ◽

Denizcan Köseoğlu ◽

Jean-François Rontani ◽

Virginie Galindo ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Spring Bloom ◽

Phytoplankton Bloom ◽

Change Point Analysis ◽

The Arctic ◽

Distribution Data ◽

Ice Melt ◽

Point Analysis ◽

The Impact

In recent years, certain mono- and di-unsaturated highly branched isoprenoid (HBI) alkene biomarkers (i.e., IP25 and HBI IIa) have emerged as useful proxies for sea ice in the Arctic and Antarctic, respectively. Despite the relatively large number of sea ice reconstructions based on IP25 and HBI IIa, considerably fewer studies have addressed HBI variability in sea ice or in the underlying water column during a spring bloom and ice melt season. In this study, we quantified IP25 and various other HBIs at high temporal and vertical resolution in sea ice and the underlying water column (suspended and sinking particulate organic matter) during a spring bloom/ice melt event in Baffin Bay (Canadian Arctic) as part of the Green Edge project. The IP25 data are largely consistent with those reported from some previous studies, but also highlight: (i) the short-term variability in its production in sea ice; (ii) the release of ice algae with high sinking rates following a switch in sea ice conditions from hyper- to hyposaline within the study period; and (iii) the occurrence of an under-ice phytoplankton bloom. Outcomes from change-point analysis conducted on chlorophyll a and IP25, together with estimates of the percentage of ice algal organic carbon in the water column, also support some previous investigations. The co-occurrence of other di- and tri-unsaturated HBIs (including the pelagic biomarker HBI III) in sea ice are likely to have originated from the diatom Berkeleya rutilans and/or the Pleurosigma and Rhizosolenia genera, residing either within the sea ice matrix or on its underside. Although a possible sea ice source for HBIs such as HBI III may also impact the use of such HBIs as pelagic counterparts to IP25 in the phytoplankton marker-IP25 index, we suggest that the impact is likely to be small based on HBI distribution data.

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Potential Consequences Of “Dirty” Arctic Sea Ice

Annals of Glaciology ◽

10.1017/s0260305500009290 ◽

1990 ◽

Vol 14 ◽

pp. 355

Author(s):

Stephanie Pfirman ◽

Manfred A. Lange ◽

Tamara S. Ledley

Keyword(s):

Sea Ice ◽

Arctic Basin ◽

Surface Melting ◽

Arctic Sea Ice ◽

The Arctic ◽

Ice Melting ◽

Large Area ◽

Sea Ice Concentration ◽

East Greenland Current ◽

Ice Surface

Observations of high particulate loads on Eurasian Basin sea ice in 1987 raise questions of consequence for sediment budgets, ice melting, ice modeling and remote sensing. Biogenic and lithogenic particles were observed in concentrations high enough to color the ice surface brown over large area (greater than 15 × 15 km2) within the Siberian branch of the Transpolar Drift stream. The sediment is most likely incorporated when ice forms on the Siberian shelf seas, and is concentrated at the ice surface after several years of summer surface melting and biological growth within the Arctic basin. Much of the particle-laden multi-year ice appears to leave the Arctic basin via Fram Strait, depositing its sediment load along the axis of the East Greenland Current. To date, variation in sea-ice particle load has not been taken into consideration when modeling ice thickness or distribution for past or future environmental scenarios, with the exception of soot deposited from nuclear war. Naturally elevated surface-particle concentration may occur if there is increased deposition from long-range or coastal transport of aeolian material, increased sediment input into sea ice which is then exposed to surface melting, and/or increased biogenic productivity on the ice surface. Such conditions may have prevailed during the Younger Dryas. If particle loads become high enough to cause extensive sea-ice melting, changes may be expected in sea-ice concentration and distribution, sea-floor sedimentation rates, and oceanic productivity.

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Transformation of Atlantic Water in the Barents Sea in winter: overview of “Transarctika-2019” cruise results

10.5194/egusphere-egu2020-11531 ◽

2020 ◽

Author(s):

Vladimir Ivanov ◽

Ivan Frolov ◽

Kirill Filchuk

Keyword(s):

Characteristic Feature ◽

Sea Ice ◽

Arctic Ocean ◽

Water Column ◽

Barents Sea ◽

Atlantic Water ◽

The Arctic ◽

The Barents Sea ◽

Open Sea ◽

The Arctic Ocean

In the recent few years the topic of accelerated sea ice loss, and related changes in the vertical structure of water masses in the East-Atlantic sector of the Arctic Ocean, including the Barents Sea and the western part of the Nansen Basin, has been in the foci of multiple studies. This region even earned the name the &#8220;Arctic warming hotspot&#8221;, due to the extreme retreat of sea ice and clear signs of change in the vertical hydrographic structure from the Arctic type to the sub-Arctic one. A gradual increase in temperature and salinity in this area has been observed since the mid-2000s. This trend is hypothetically associated with a general decrease in the volume of sea ice in the Arctic Ocean, which leads to a decrease of ice import in the Barents Sea, salinization, weakening of density stratification, intensification of vertical mixing and an increase of heat and salt fluxes from the deep to the upper mixed layer. The result of such changes is a further reduction of sea ice, i.e. implementation of positive feedback, which is conventionally refereed as the &#8220;atlantification. Due to the fact that the Barents Sea is a relatively shallow basin, the process of atlantification might develop here much faster than in the deep Nansen Basin. Thus, theoretically, the hydrographic regime in the northern part of the Barents Sea may rapidly transform to a &#8220;Nordic Seas &#8211; wise&#8221;, a characteristic feature of which is the year-round absence of the ice cover with debatable consequences for the climate and ecosystem of the region and adjacent land areas. Due to the obvious reasons, historical observations in the Barents Sea mostly cover the summer season. Here we present a rare oceanographic data, collected during the late winter - early spring in 2019. Measurements were occupied at four sequential oceanographic surveys from the boundary between the Norwegian Sea and the Barents Sea &#8211; the so called Barents Sea opening to the boundary between the Barents Sea and the Kara Sea. Completed hydrological sections allowed us to estimate the contribution of the winter processes in the Atlantic Water transformation at the end of the winter season. Characteristic feature of the observed transformation is the homogenization of the near-to-bottom part of the water column with remaining stratification in the upper part. A probable explanation of such changes is the dominance of shelf convection and cascading of dense water over the open sea convection. In this case, complete homogenization of the water column does not occur, since convection in the open sea is impeded by salinity and density stratification, which is maintained by melting of the imported sea ice in the relatively warm water. The study was supported by RFBR grant # 18-05-60083.

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