scholarly journals The importance of turbulent ocean-sea ice nutrient exchanges for simulation of ice algal biomass and production with CICE6.1 and Icepack 1.2

2021 ◽  
Author(s):  
Pedro Duarte ◽  
Philipp Assmy ◽  
Karley Campbell ◽  
Arild Sundfjord
Keyword(s):  
Sea Ice ◽  
Algal Blooms ◽  
Molecular Diffusion ◽  
Critical Role ◽  
The Arctic ◽  
Algal Production ◽  
Biogeochemical Models ◽  
Momentum And Heat Transfer ◽  
Turbulent Momentum ◽  
Heat Exchanges

Abstract. Different sea-ice models apply unique approaches in the computation of nutrient diffusion between the ocean and the ice bottom, which are generally decoupled from the calculation of turbulent momentum and heat flux. Often, a simple molecular diffusion formulation is used. We argue that nutrient transfer from the ocean to sea ice should be as consistent as possible with momentum and heat transfer, since all these fluxes respond to varying forcing in a similar fashion. We hypothesize that biogeochemical models which do not consider such turbulent nutrient exchanges between the ocean and the sea-ice underestimate bottom-ice algal production. The Los Alamos Sea Ice Model (CICE + Icepack) was used to test this hypothesis by comparing simulations with molecular and turbulent diffusion of nutrients into the bottom of sea ice, implemented in a way that is consistent with turbulent momentum and heat exchanges. Simulation results support the hypothesis, showing a significant enhancement of ice algal production and biomass when nutrient limitation was relieved by bottom-ice turbulent exchange. Our results emphasize the potentially critical role of turbulent exchanges to sea ice algal blooms, and the importance of thus properly representing them in biogeochemical models. The relevance of this becomes even more apparent considering ongoing trends in the Arctic Ocean, with a predictable shift from light to nutrient limited growth of ice algae earlier in the spring, as the sea ice becomes more fractured and thinner with a larger fraction of young ice with thin snow cover.

Sea-ice algal phenology in a warmer Arctic

2020 ◽  
Author(s):  
Letizia Tedesco ◽  
Marcello Vichi ◽  
Enrico Scoccimarro
Keyword(s):  
Sea Ice ◽  
Algal Blooms ◽  
Climate Models ◽  
Time Windows ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Biological Time ◽  
Algal Productivity ◽  
The Impact

<p>The Arctic sea-ice decline is among the most emblematic manifestations of climate change and is occurring before we understand its ecological consequences. We investigated future changes in algal productivity combining a biogeochemical model for sympagic algae with sea-ice drivers from an ensemble of 18 CMIP5 climate models. Model projections indicate quasi-linear physical changes along latitudes but markedly nonlinear response of sympagic algae, with distinct latitudinal patterns. While snow cover thinning explains the advancement of algal blooms below 66°N, narrowing of the biological time windows yields small changes in the 66°N to 74°N band, and shifting of the ice seasons toward more favorable photoperiods drives the increase in algal production above 74°N. These diverse latitudinal responses indicate that the impact of declining sea ice on Arctic sympagic production is both large and complex, with consequent trophic and phenological cascades expected in the rest of the food web.</p>

scholarly journals Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

2013 ◽  
Vol 43 (5) ◽  
pp. 863-883 ◽  
Author(s):  
Ian Fenty ◽  
Patrick Heimbach
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Critical Role ◽  
The Arctic ◽  
Labrador Sea ◽  
Upper Ocean ◽  
Quasi Equilibrium ◽  
Low Salinity ◽  
Thermohaline Front ◽  
Subsurface Waters

Abstract This study investigates the hydrographic processes involved in setting the maximum wintertime sea ice (SI) extent in the Labrador Sea and Baffin Bay. The analysis is based on an ocean and sea ice state estimate covering the summer-to-summer 1996/97 annual cycle. The estimate is a synthesis of in situ and satellite hydrographic and ice data with a regional coupled ⅓° ocean–sea ice model. SI advective processes are first demonstrated to be required to reproduce the observed ice extent. With advection, the marginal ice zone (MIZ) location stabilizes where ice melt balances ice mass convergence, a quasi-equilibrium condition achieved via the convergence of warm subtropical-origin subsurface waters into the mixed layer seaward of the MIZ. An analysis of ocean surface buoyancy fluxes reveals a critical role of low-salinity upper ocean (100 m) anomalies for the advancement of SI seaward of the Arctic Water–Irminger Water Thermohaline Front. Anomalous low-salinity waters slow the rate of buoyancy loss–driven mixed layer deepening, shielding an advancing SI pack from the warm subsurface waters, and are conducive to a positive surface meltwater stabilization enhancement (MESEM) feedback driven by SI meltwater release. The low-salinity upper-ocean hydrographic conditions in which the MESEM efficiently operates are termed sea ice–preconditioned waters (SIPW). The SI extent seaward of the Thermohaline Front is shown to closely correspond to the distribution of SIPW. The analysis of two additional state estimates (1992/93, 2003/04) suggests that interannual hydrographic variability provides a first-order explanation for SI maximum extent anomalies in the region.

scholarly journals Effect of frequent winter warming events (storms) and snow on sea-ice growth – a case from the Atlantic sector of the Arctic Ocean during the N-ICE2015 campaign

2020 ◽  
Vol 61 (82) ◽  
pp. 164-170
Author(s):  
Ioanna Merkouriadi ◽  
Bin Cheng ◽  
Stephen R. Hudson ◽  
Mats A. Granskog
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Critical Role ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Winter Period ◽  
Storm Events ◽  
Atlantic Sector ◽  
Ice Growth ◽  
Arctic Sea

AbstractWe examine the relative effect of warming events (storms) and snow cover on thermodynamic growth of Arctic sea ice in winter. We use a 1-D snow and ice thermodynamic model to perform sensitivity experiments. Observations from the winter period of the Norwegian young sea ICE (N-ICE2015) campaign north of Svalbard are used to initiate and force the model. The N-ICE2015 winter was characterized by frequent storm events that brought pulses of heat and moisture, and a thick snow cover atop the sea ice (0.3–0.5 m). By the end of the winter, sea-ice bottom growth was negligible. We show that the thermodynamic effect of storms to the winter sea-ice growth is controlled by the amount of snow on sea ice. For 1.3 m initial ice thickness, the decrease in ice growth caused by the warming events ranged from −1.4% (for 0.5 m of snow) to −7.5% (for snow-free conditions). The decrease in sea-ice growth caused by the thick snow (0.5 m) was more important, ranging from −17% (with storms) to −23% (without storms). The results showcase the critical role of snow on winter Arctic sea-ice growth.

Manual point-measurements of sea ice mass balance during the MOSAiC Expedition

2021 ◽  
Author(s):  
Ian Raphael ◽  
Donald Perovich ◽  
Chris Polashenski ◽  
David Clemens-Sewall ◽  
Polona Itkin ◽  
...  
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Mass Balance ◽  
Critical Role ◽  
The Arctic ◽  
Diverse Range ◽  
Individual Measurement ◽  
Ice Surface ◽  
Ice Mass Balance ◽  
Ocean Measurements

<p>Sea ice plays a critical role in the Arctic climate system, regulating much of the energy transfer between the ocean and the atmosphere. Repeat measurements of ice mass balance at discrete points allow us to determine the direct response of sea ice mass to environmental conditions. We installed a network of mass balance measurement sites across the MOSAiC Central Observatories, distributed over a diverse range of ice types and features. The sites were composed of gridded arrays of 9-17 hotwire thickness gauges, each paired with a surface ablation stake. Seven sites were installed on first year ice, and seven on second or multi year ice, with a total of 120+ individual measurement stations. The sites were operational over different periods throughout the year; several were destroyed or became inaccessible during ridging events. Initial ice thicknesses ranged from 0.13-3.50 m. We made measurements of ice and snow interfaces and thicknesses with 1 cm precision at each station, at intervals of 2-3 weeks during the growth season and as few as 1-2 days during the melt season. From these measurements, we infer ice growth, ice bottom melt, ice surface melt, snow deposition, snow erosion, and snow melt. The time series spans October 2019–September 2020, with a five-week measurement gap beginning mid-May 2020. We present an overview of the measurements and preliminary analysis, partitioning results by ice type and comparing mass balance to concurrent atmosphere and ocean measurements. We identify trends in the seasonal evolution of different ice types, and give particular attention to notable events in the time series. As true point-measurements, the data are especially relevant in improving one-dimensional thermodynamic sea ice models. The results also provide validation for satellite and electromagnetic induction ice-thickness measurements made during MOSAiC, which offer higher areal coverage but lower measurement- and spatial-precision.</p>

The dawn of Molecular Genetics in Paleoceanography: tracing Arctic change during the Holocene with marine sedaDNA records from Greenland

2020 ◽  
Author(s):  
Sofia Ribeiro ◽  
Sara Hardardottir ◽  
Jessica Louise Ray ◽  
Stijn De Schepper ◽  
Audrey Limoges ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Full Range ◽  
Sediment Cores ◽  
Critical Role ◽  
Genetic Material ◽  
Digital Pcr ◽  
The Arctic ◽  
Taxonomic Resolution ◽  
Gene Copy

<p>As we move towards a “blue” Arctic Ocean in the summer within the next decades, predicting the full range of effects of climate change on the marine arctic environment remains a challenge. This is partly due to the paucity of long-term data on ocean-biosphere-cryosphere interactions over time and partly because, today, much of our knowledge on past ocean variability derives from microfossil and biogeochemical tracers that all have considerable limitations such as preservation biases and low taxonomic resolution or coverage.</p><p>Recent studies have revealed sedaDNA as a potential “game-changer” in our ability to reconstruct past ocean conditions, due to the preservation of DNA at low temperatures, and the possibility to capture a much larger fraction of the Arctic marine biome diversity than with classical approaches. However, while sedaDNA has been used in terrestrial, archeological, and lake studies for some years, its application to marine sediment records is still in its infancy.</p><p>Here, we will present new results from material recently collected along the two Arctic Ocean outflow shelves off Greenland (Greenland Sea/Fram Strait and Northern Baffin Bay/Nares Strait). We have used a combination of modern and ancient DNA methods applied to seawater, surface sediments, and sediment cores covering the past ca. 12 000 years with the objectives of: 1) characterizing the vertical export of sea ice-associated genetic material through the water column and into the sediments following sea ice melt and 2) exploring the potential of sedaDNA from the circum-polar sea ice dinoflagellate Polarella glacialis as a new sea ice proxy. For the first objective, we followed a comparative metabarcoding approach while the second objective included designing species-specific primers followed by gene copy number quantification by a droplet digital PCR assay. </p><p>We argue that sedaDNA will have a critical role in expanding the Paleoceanography “toolbox” and lead to the establishment of a new cross-disciplinary field.</p><p> </p>

scholarly journals Critical role of snow on sea ice growth in the Atlantic sector of the Arctic Ocean

2018 ◽  
Author(s):  
Mats Granskog ◽  
Ioanna Merkouriadi ◽  
Bin Cheng ◽  
Robert M. Graham ◽  
Anja Rösel
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Critical Role ◽  
The Arctic ◽  
Atlantic Sector ◽  
Ice Growth ◽  
The Arctic Ocean

scholarly journals Stress factors resulting from the Arctic vernal sea-ice melt

Elem Sci Anth ◽  
2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Rémi Amiraux ◽  
Christopher Burot ◽  
Patricia Bonin ◽  
Guillaume Massé ◽  
Sophie Guasco ◽  
...  
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Salinity Stress ◽  
Bacterial Activity ◽  
The Arctic ◽  
Algal Production ◽  
Isomerase Activity ◽  
Ice Melt ◽  
Sinking Particles ◽  
Algal Material

During sea-ice melt in the Arctic, primary production by sympagic (sea-ice) algae can be exported efficiently to the seabed if sinking rates are rapid and activities of associated heterotrophic bacteria are limited. Salinity stress due to melting ice has been suggested to account for such low bacterial activity. We further tested this hypothesis by analyzing samples of sea ice and sinking particles collected from May 18 to June 29, 2016, in western Baffin Bay as part of the Green Edge project. We applied a method not previously used in polar regions—quantitative PCR coupled to the propidium monoazide DNA-binding method—to evaluate the viability of bacteria associated with sympagic and sinking algae. We also measured cis-trans isomerase activity, known to indicate rapid bacterial response to salinity stress in culture studies, as well as free fatty acids known to be produced by algae as bactericidal compounds. The viability of sympagic-associated bacteria was strong in May (only approximately 10% mortality of total bacteria) and weaker in June (average mortality of 43%; maximum of 75%), with instances of elevated mortality in sinking particle samples across the time series (up to 72%). Short-term stress reflected by cis-trans isomerase activity was observed only in samples of sinking particles collected early in the time series. Following snow melt, however, and saturating levels of photosynthetically active radiation in June, we observed enhanced ice-algal production of bactericidal compounds (free palmitoleic acid; up to 4.8 mg L–1). We thus suggest that protection of sinking sympagic material from bacterial degradation early in a melt season results from low bacterial activity due to salinity stress, while later in the season, algal production of bactericidal compounds induces bacterial mortality. A succession of bacterial stressors during Arctic ice melt helps to explain the efficient export of sea-ice algal material to the seabed.

scholarly journals Microalgal community structure and primary production in Arctic and Antarctic sea ice: A synthesis

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Maria A. van Leeuwe ◽  
Letizia Tedesco ◽  
Kevin R. Arrigo ◽  
Philipp Assmy ◽  
Karley Campbell ◽  
...  
Keyword(s):  
Community Structure ◽  
Sea Ice ◽  
Climate Models ◽  
Ice Cores ◽  
The Arctic ◽  
Small Scale ◽  
Low Carbon ◽  
Bottom Communities ◽  
Biogeochemical Models ◽  
Microalgal Community

Sea ice is one the largest biomes on earth, yet it is poorly described by biogeochemical and climate models. In this paper, published and unpublished data on sympagic (ice-associated) algal biodiversity and productivity have been compiled from more than 300 sea-ice cores and organized into a systematic framework. Significant patterns in microalgal community structure emerged from this framework. Autotrophic flagellates characterize surface communities, interior communities consist of mixed microalgal populations and pennate diatoms dominate bottom communities. There is overlap between landfast and pack-ice communities, which supports the hypothesis that sympagic microalgae originate from the pelagic environment. Distribution in the Arctic is sometimes quite different compared to the Antarctic. This difference may be related to the time of sampling or lack of dedicated studies. Seasonality has a significant impact on species distribution, with a potentially greater role for flagellates and centric diatoms in early spring. The role of sea-ice algae in seeding pelagic blooms remains uncertain. Photosynthesis in sea ice is mainly controlled by environmental factors on a small scale and therefore cannot be linked to specific ice types. Overall, sea-ice communities show a high capacity for photoacclimation but low maximum productivity compared to pelagic phytoplankton. Low carbon assimilation rates probably result from adaptation to extreme conditions of reduced light and temperature in winter. We hypothesize that in the near future, bottom communities will develop earlier in the season and develop more biomass over a shorter period of time as light penetration increases due to the thinning of sea ice. The Arctic is already witnessing changes. The shift forward in time of the algal bloom can result in a mismatch in trophic relations, but the biogeochemical consequences are still hard to predict. With this paper we provide a number of parameters required to improve the reliability of sea-ice biogeochemical models.

scholarly journals Wind-driven interannual variability of sea ice algal production in the western Arctic Chukchi Borderland

2015 ◽  
Vol 12 (20) ◽  
pp. 6147-6168 ◽  
Author(s):  
E. Watanabe ◽  
J. Onodera ◽  
N. Harada ◽  
M. N. Aita ◽  
A. Ishida ◽  
...  
Keyword(s):  
Sea Ice ◽  
Interannual Variability ◽  
Sediment Trap ◽  
Particle Flux ◽  
The Arctic ◽  
Ice Algae ◽  
Algal Production ◽  
Western Arctic ◽  
Chukchi Borderland ◽  
Sinking Flux

Abstract. Seasonal and interannual variability in the biogenic particle sinking flux was recorded using multi-year bottom-tethered sediment trap mooring systems in the Northwind Abyssal Plain (Station NAP: 75° N, 162° W, 1975 m water depth) of the western Arctic Chukchi Borderland. Trapped particle flux at a median depth of 184 m had an obvious peak and dominance of sea ice-related diatom assemblages in August 2011. The observed particle flux was considerably suppressed throughout summer 2012. In the present study, the response of ice algal production and biomass to wind-driven changes in the physical environment was addressed using a pan-Arctic sea ice–ocean modeling approach. A sea ice ecosystem with ice algae was newly incorporated into the lower-trophic marine ecosystem model, which was previously coupled with a high-resolution (i.e., 5 km horizontal grid size) sea ice–ocean general circulation model. Seasonal model experiments covering 2-year mooring periods indicated that primary productivity of ice algae around the Chukchi Borderland depended on basin-scale wind patterns via various processes. Easterly winds in the southern part of a distinct Beaufort High supplied nutrient-rich water for euphotic zones of the NAP region via both surface Ekman transport of Chukchi shelf water and vertical turbulent mixing with underlying nutricline water in 2011. In contrast, northwesterly winds flowing in the northern part of an extended Siberian High transported oligotrophic water within the Beaufort Gyre circulation toward the NAP region in 2012. The modeled ice algal biomass during summer reflected the differences in nutrient distribution. The modeled sinking flux of particulate organic nitrogen (PON) was comparable with the time series obtained from sediment trap data in summer 2011. In contrast, lateral advection of ice algal patches of shelf origin during a great cyclone event may have caused a modeled PON flux bias in 2012. Sensitivity experiments revealed several uncertainties of model configurations of ice algal productivity, particle sinking speed, and grazing activities. Extending the year-long measurements is expected to help illustrate the more general features of ice-related biological processes in the Arctic Ocean.

scholarly journals Sea-ice algal phenology in a warmer Arctic

2019 ◽  
Vol 5 (5) ◽  
pp. eaav4830 ◽  
Author(s):  
L. Tedesco ◽  
M. Vichi ◽  
E. Scoccimarro
Keyword(s):  
Sea Ice ◽  
Algal Blooms ◽  
Climate Models ◽  
Time Windows ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Biological Time ◽  
Algal Productivity ◽  
The Impact

The Arctic sea-ice decline is among the most emblematic manifestations of climate change and is occurring before we understand its ecological consequences. We investigated future changes in algal productivity combining a biogeochemical model for sympagic algae with sea-ice drivers from an ensemble of 18 CMIP5 climate models. Model projections indicate quasi-linear physical changes along latitudes but markedly nonlinear response of sympagic algae, with distinct latitudinal patterns. While snow cover thinning explains the advancement of algal blooms below 66°N, narrowing of the biological time windows yields small changes in the 66°N to 74°N band, and shifting of the ice seasons toward more favorable photoperiods drives the increase in algal production above 74°N. These diverse latitudinal responses indicate that the impact of declining sea ice on Arctic sympagic production is both large and complex, with consequent trophic and phenological cascades expected in the rest of the food web.

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