scholarly journals 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 ◽  
2019 ◽  
Vol 7 ◽  
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.

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

2017 ◽  
Vol 14 (12) ◽  
pp. 3129-3155 ◽  
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.

scholarly journals The impact of melt ponds on summertime microwave brightness temperatures and sea ice concentrations

2016 ◽  
Author(s):  
S. Kern ◽  
A. Rösel ◽  
L. T. Pedersen ◽  
N. Ivanova ◽  
R. Saldo ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Water Fraction ◽  
Microwave Brightness Temperature ◽  
Ice Melt ◽  
Melt Ponds ◽  
Retrieval Algorithms ◽  
The Impact

Abstract. The sea ice concentration (SIC) derived from satellite microwave brightness temperature (TB) data are known to be less accurate during summer melt conditions – in the Arctic Ocean primarily because of the impact of melt ponds on sea ice. Using data from June to August 2009, we investigate how TBs and SICs vary as a function of the ice surface fraction (ISF) computed from open water fraction and melt pond fraction both derived from satellite optical reflectance data. SIC is computed from TBs using a set of eight different retrieval algorithms and applying a consistent set of tie points. We find that TB values change during sea ice melt non-linearly and not monotonically as a function of ISF for ISF of 50 to 100 %. For derived parameters such as the polarization ratio at 19 GHz the change is monotonic but substantially smaller than theoretically expected. Changes in ice/snow radiometric properties during melt also contribute to the TB changes observed; these contributions are functions of frequency and polarization and have the potential to partly counter-balance the impact of changing ISF on the observed TBs. All investigated SIC retrieval algorithms overestimate ISF when using winter tie points. The overestimation varies among the algorithms as a function of ISF such that the SIC retrieval algorithms could be categorized into two different classes. These reveal a different degree of ISF overestimation at high ISF and an opposite development of ISF over-estimation as ISF decreases. For one class, correlations between SIC and ISF are ≥ 0.85 and the associated linear regression lines suggest an exploitable relationship between SIC and ISF if reliable summer sea ice tie points can be established. This study shows that melt ponds are interpreted as open water by the SIC algorithms, while the concentration of ice between the melt ponds is in general being overestimated. These two effects may cancel each other out and thus produce seemingly correct SIC for the wrong reasons. This cancelling effect will in general only be "correct" at one specific value of MPF. Based on our findings we recommend to not correct SIC algorithms for the impact of melt ponds as this seems to violate physical principles. Users should be aware that the SIC algorithms available at the moment retrieve a combined parameter presented by SIC in winter and ISF in summer.

scholarly journals Cyclone impact on sea ice in the central Arctic Ocean: a statistical study

2014 ◽  
Vol 8 (1) ◽  
pp. 303-317 ◽  
Author(s):  
A. Kriegsmann ◽  
B. Brümmer
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Model ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
Cumulative Impact ◽  
Model Composite ◽  
Ice Melt ◽  
The Arctic Ocean ◽  
The Impact

Abstract. This study investigates the impact of cyclones on the Arctic Ocean sea ice for the first time in a statistical manner. We apply the coupled ice–ocean model NAOSIM which is forced by the ECMWF analyses for the period 2006–2008. Cyclone position and radius detected in the ECMWF data are used to extract fields of wind, ice drift, and concentration from the ice–ocean model. Composite fields around the cyclone centre are calculated for different cyclone intensities, the four seasons, and different sub-regions of the Arctic Ocean. In total about 3500 cyclone events are analyzed. In general, cyclones reduce the ice concentration in the order of a few percent increasing towards the cyclone centre. This is confirmed by independent AMSR-E satellite data. The reduction increases with cyclone intensity and is most pronounced in summer and on the Siberian side of the Arctic Ocean. For the Arctic ice cover the cumulative impact of cyclones has climatologic consequences. In winter, the cyclone-induced openings refreeze so that the ice mass is increased. In summer, the openings remain open and the ice melt is accelerated via the positive albedo feedback. Strong summer storms on the Siberian side of the Arctic Ocean may have been important contributions to the recent ice extent minima in 2007 and 2012.

scholarly journals Cyclone impact on sea ice in the central Arctic Ocean: a statistical study

2013 ◽  
Vol 7 (2) ◽  
pp. 1141-1176 ◽  
Author(s):  
A. Kriegsmann ◽  
B. Brümmer
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Ocean Model ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
Model Composite ◽  
Ice Melt ◽  
The Arctic Ocean ◽  
Arctic Ice ◽  
The Impact

Abstract. This study investigates the impact of cyclones on the Arctic Ocean sea ice for the first time in a statistical manner. We apply the coupled ice–ocean model NAOSIM which is forced by the ECMWF analyses for the period 2006–2008. Cyclone position and radius detected in the ECMWF data are used to extract fields of wind, ice drift, and concentration from the ice–ocean model. Composite fields around the cyclone centre are calculated for different cyclone intensities, the four seasons, and different regions of the Arctic Ocean. In total about 3500 cyclone events are analyzed. In general, cyclones reduce the ice concentration on the order of a few percent increasing towards the cyclone centre. This is confirmed by independent AMSR-E satellite data. The reduction increases with cyclone intensity and is most pronounced in summer and on the Siberian side of the Arctic Ocean. For the Arctic ice cover the impact of cyclones has climatologic consequences. In winter, the cyclone-induced openings refreeze so that the ice mass is increased. In summer, the openings remain open and the ice melt is accelerated via the positive albedo feedback. Strong summer storms on the Siberian side of the Arctic Ocean may have been important reasons for the recent ice extent minima in 2007 and 2012.

scholarly journals The impact of sea ice regime on meiobenthic structure and function north of Svalbard

2018 ◽  
Author(s):  
Katarzyna Grzelak ◽  
Monika Kędra ◽  
Klaudia Gregorczyk ◽  
Nathalie Morata ◽  
Magdalena Blazewicz
Keyword(s):  
Sea Ice ◽  
Phytoplankton Bloom ◽  
Standing Stock ◽  
Arctic Region ◽  
The Arctic ◽  
Life Strategy ◽  
Nematode Diversity ◽  
Rapid Transition ◽  
And Function ◽  
The Impact

Eight stations located in the seasonal sea ice zone north of Svalbard were investigated during ‘TRANSSIZ’ cruise within Arctic in Rapid Transition initiative. Nematodes were used as a key group within the meiofauna. Our study provides previously unavailable data on nematode diversity for this Arctic region during ecologically important spring to summer transition time. Phytoplankton bloom development is crucial for the Arctic marine ecosystems functioning, yet data from this time of year, particularly for the deep-sea basins north of Svalbard are still scarce. The obtained results suggest that nematode community differences are attributed to prevailing environmental conditions, ice-edge related bloom-phase. Three distinct nematode assemblages were observed and were related to bloom stage. Nematodes standing stock and diversity was the lowest at stations where pre-bloom phase occurred. Community was dominated by opportunistic genera belonging to Monhysteridae and by Acantholaimus. Conditions at stations with already developed bloom promoted enhanced abundance and biomass of nematodes and almost two time higher number of nematode genera in comparison to pre-bloom stations. Communities at those stations were characterized by genera of Desmoscolecidae family. Stations with early-bloom conditions appeared as transitional, with conditions in which relatively high number of genera with different life strategy can co-exist. The study was completed thanks to funding provided by the National Science Centre, Poland (grant no. 2016/20/S/NZ8/00432 and 2015/19/B/NZ8/03945). Presented material was collected during R/V Polarstern TRANSSIZ cruise (ARK XXIX/1; PS92), carried out under grant number AWI_PS92_00 and organized by Arctic in Rapid Transition (ART).

scholarly journals Processes controlling aggregate formation and distribution during the Arctic phytoplankton spring bloom in Baffin Bay

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Jordan Toullec ◽  
Brivaëla Moriceau ◽  
Dorothée Vincent ◽  
Lionel Guidi ◽  
Augustin Lafond ◽  
...  
Keyword(s):  
Sea Ice ◽  
Spring Bloom ◽  
Phytoplankton Bloom ◽  
Light Availability ◽  
Open Water ◽  
The Arctic ◽  
Phytoplankton Production ◽  
Baffin Bay ◽  
Migration Pathway ◽  
Phytoplankton Cells

In the last decades, the Arctic Ocean has been affected by climate change, leading to alterations in the sea ice cover that influence the phytoplankton spring bloom, its associated food web, and therefore carbon sequestration. During the Green Edge 2016 expedition in the central Baffin Bay, the phytoplankton spring bloom and its development around the ice edge was followed along 7 transects from open water to the ice-pack interior. Here, we studied some of the processes driving phytoplankton aggregation, using aggregate and copepod distribution profiles obtained with an underwater vision profiler deployed at several stations along the transects. Our results revealed a sequential pattern during sea ice retreat in phytoplankton production and in aggregate production and distribution. First, under sea ice, phytoplankton started to grow, but aggregates were not formed. Second, after sea ice melting, phytoplankton (diatoms and Phaeocystis spp. as the dominant groups) benefited from the light availability and stratified environment to bloom, and aggregation began coincident with nutrient depletion at the surface. Third, maxima of phytoplankton aggregates deepened in the water column and phytoplankton cells at the surface began to degrade. At most stations, silicate limitation began first, triggering aggregation of the phytoplankton cells; nitrate limitation came later. Copepods followed aggregates at the end of the phytoplankton bloom, possibly because aggregates provided higher quality food than senescing phytoplankton cells at the surface. These observations suggest that aggregation is involved in 2 export pathways constituting the biological pump: the gravitational pathway through the sinking of aggregates and fecal pellets and the migration pathway when zooplankton follow aggregates during food foraging.

scholarly journals The impact of sea ice regime on meiobenthic structure and function north of Svalbard

2018 ◽  
Author(s):  
Katarzyna Grzelak ◽  
Monika Kędra ◽  
Klaudia Gregorczyk ◽  
Nathalie Morata ◽  
Magdalena Blazewicz
Keyword(s):  
Sea Ice ◽  
Phytoplankton Bloom ◽  
Standing Stock ◽  
Arctic Region ◽  
The Arctic ◽  
Life Strategy ◽  
Nematode Diversity ◽  
Rapid Transition ◽  
And Function ◽  
The Impact

Eight stations located in the seasonal sea ice zone north of Svalbard were investigated during ‘TRANSSIZ’ cruise within Arctic in Rapid Transition initiative. Nematodes were used as a key group within the meiofauna. Our study provides previously unavailable data on nematode diversity for this Arctic region during ecologically important spring to summer transition time. Phytoplankton bloom development is crucial for the Arctic marine ecosystems functioning, yet data from this time of year, particularly for the deep-sea basins north of Svalbard are still scarce. The obtained results suggest that nematode community differences are attributed to prevailing environmental conditions, ice-edge related bloom-phase. Three distinct nematode assemblages were observed and were related to bloom stage. Nematodes standing stock and diversity was the lowest at stations where pre-bloom phase occurred. Community was dominated by opportunistic genera belonging to Monhysteridae and by Acantholaimus. Conditions at stations with already developed bloom promoted enhanced abundance and biomass of nematodes and almost two time higher number of nematode genera in comparison to pre-bloom stations. Communities at those stations were characterized by genera of Desmoscolecidae family. Stations with early-bloom conditions appeared as transitional, with conditions in which relatively high number of genera with different life strategy can co-exist. The study was completed thanks to funding provided by the National Science Centre, Poland (grant no. 2016/20/S/NZ8/00432 and 2015/19/B/NZ8/03945). Presented material was collected during R/V Polarstern TRANSSIZ cruise (ARK XXIX/1; PS92), carried out under grant number AWI_PS92_00 and organized by Arctic in Rapid Transition (ART).

Assessment of relationships between Arctic sea ice and stratification of water column modelled by NEMO version 4.0

2020 ◽  
Author(s):  
Byoung Woong An ◽  
Pil-Hun Chang
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Chukchi Sea ◽  
Numerical Models ◽  
Forecast Accuracy ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Sea Ice Extent ◽  
Arctic Sea ◽  
The Impact

<p>The Arctic Ocean is globally important for the weather and climate and has a unique environment. Therefore accurate prediction of the Arctic sea ice remains crucial in most numerical models. It is because small changes within the atmosphere or the ocean can cause major changes in the areal extent and thickness of the sea ice. Such changes, in turn, will have pronounced effects on the ocean and atmosphere through modification of the albedo, the ocean-atmosphere heat and momentum exchanges, and the ocean-ice heat and salt fluxes. The focus of this study is on the impact of such coupling on sea ice and upper ocean properties and the halostad related sea ice variations and inflows from Oceans. To assess the impact of the vertical mixing, we perform a set of sensitivity experiments with a global oceanic configuration at 1/4° resolution based on the version 4.0 of NEMO (Nucleus for European Modelling of the Ocean). In particular we examine the spatio-temporal distributions of Pacific and Eastern Arctic origin waters in the Chukchi Sea using 2016-2018 hydrographic data. Overall, the model agrees well with observations in terms of sea ice extent in spite of inaccurate vertical stratification of the water column. We conclude that beyond seasonal time scale forecast accuracy could be improved by more accurate representation of the structure of water masses.</p>

The impact of shallow stratification on air-sea CO2 flux in the summer Arctic Ocean

2021 ◽  
Author(s):  
Yuanxu Dong ◽  
Dorothee Bakker ◽  
Thomas Bell ◽  
Peter Liss ◽  
Ian Brown ◽  
...  
Keyword(s):  
Surface Water ◽  
Wind Speed ◽  
Sea Ice ◽  
Surface Temperature ◽  
Arctic Ocean ◽  
The Arctic ◽  
Near Surface ◽  
Ice Melt ◽  
The Arctic Ocean ◽  
The Impact

<p>Air-sea carbon dioxide (CO<sub>2</sub>) flux is often indirectly estimated by the bulk method using the i<em>n-situ</em> air-sea difference in CO<sub>2</sub> fugacity and a wind speed dependent parameterisation of the gas transfer velocity (<em>K</em>). In the summer, sea-ice melt in the Arctic Ocean generates strong shallow stratification with significant gradients in temperature, salinity, dissolved inorganic carbon (DIC) and alkalinity (TA), and thus a near-surface CO<sub>2</sub> fugacity  (<em>f</em>CO<sub>2w</sub>) gradient. This gradient can cause an error in bulk air-sea CO<sub>2</sub> flux estimates when the <em>f</em>CO<sub>2w</sub> is measured by the ship’s underway system at ~5 m depth. Direct air-sea CO<sub>2</sub> flux measurement by eddy covariance (EC) is free from the impact of shallow stratification because the EC CO<sub>2</sub> flux does not rely on a <em>f</em>CO<sub>2w</sub> measurement. In this study, we use summertime EC flux measurements from the Arctic Ocean to back-calculate the sea surface <em>f</em>CO<sub>2w</sub> and temperature and compare them with the underway measurements. We show that the EC air-sea CO<sub>2</sub> flux agrees well with the bulk flux in areas less likely to be influenced by ice melt (salinity > 32). However, in regions with salinity less than 32, the underway <em>f</em>CO<sub>2w</sub> is higher than the EC estimate of surface <em>f</em>CO<sub>2w</sub> and thus the bulk estimate of ocean CO<sub>2</sub> uptake is underestimated. The <em>f</em>CO<sub>2w</sub> difference can be partly explained by the surface to sub-surface temperature difference. The EC estimate of surface temperature is lower than the sub-surface water temperature and this difference is wind speed-dependent. Upper-ocean salinity gradients from CTD profiles suggest likely difference in DIC and TA concentrations between the surface and sub-surface water. These DIC and TA gradients likely explain much of the near-surface <em>f</em>CO<sub>2w</sub> gradient. Accelerating summertime loss of sea ice results in additional meltwater, which enhances near-surface stratification and increases the uncertainty of bulk air-sea CO<sub>2</sub> flux estimates in polar regions.</p>

Freshwater under the MOSAiC floe: implications of under-ice melt ponds for mass balance

2021 ◽  
Author(s):  
Madison Smith ◽  
Luisa von Albedyll ◽  
Ian Raphael ◽  
Ilkka Matero ◽  
Benjamin A. Lange
Keyword(s):  
Sea Ice ◽  
Mass Balance ◽  
Early Summer ◽  
The Arctic ◽  
Ice Melt ◽  
Freshwater Ponds ◽  
Ice Floes ◽  
Freshwater Inputs ◽  
June July ◽  
The Impact

<p>During the melt season in the Arctic, freshwater ponds can accumulate under ice floes as a result of local snow and sea ice melt, far from terrestrial freshwater inputs. Under-ice freshwater ponds have been suggested to play a role in the summer sea ice mass balance both by isolating the sea ice from salty, warmer water below, and by driving formation of ice ‘false bottoms’ at the interface of the under-ice pond and the underlying ocean. </p><p>The MOSAiC drift expedition in the Central Arctic observed the presence of under-ice ponds and false bottoms beginning early in the melt season (June - July) at primarily first-year ice locations on the floe. We examine the prevalence and drivers of these ponds and resulting false bottoms during this period. Additionally, we explore the impact for mass balance using observations from ablation stakes and a 1D model, where freshwater ponds can not only delay summer melt but also result in growth. We speculate that the unique history of the MOSAiC floe likely led to a relatively high occurrence of these features, but the results also suggest that freshwater under-ice ponds and false bottoms may be more common and more persistent in early summer in the Arctic than previously thought. Both have implications for the broader ice-ocean system, for example by reducing fluxes between the ice and the ocean, isolating the primary producers in ice from pelagic nutrient sources, and altering the optical properties.</p>

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