scholarly journals Enhanced bottom-ice algal biomass across a tidal strait in the Kitikmeot Sea of the Canadian Arctic

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
Laura A. Dalman ◽  
Brent G. T. Else ◽  
David Barber ◽  
Eddy Carmack ◽  
William J. Williams ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Chlorophyll A ◽  
Stoichiometric Composition ◽  
Open Water ◽  
Taxonomic Composition ◽  
Water Dynamics ◽  
Algal Community ◽  
The Arctic ◽  
First Year ◽  
Ice Algae

Sea ice algae are an important contributor of primary production in the Arctic ecosystem. Within the bottom-ice environment, access to nutrients from the underlying ocean is a major factor controlling production, phenology, and taxonomic composition of ice algae. Previous studies have demonstrated that tides and currents play an important role in driving the flux of nutrients to bottom-ice algal communities when biological demand during the spring bloom is high. In this study we investigate how surface currents under landfast first-year ice influence nutrient supply based on stoichiometric composition, algal chlorophyll a biomass and species composition during spring 2016, in Dease Strait, Nunavut. Stronger water dynamics over a shoaled and constricted strait dominated by tidal currents (tidal strait) supported turbulent flow more than 85% of the deployment duration in comparison to outside the tidal strait in an embayment where turbulent flow was only evidenced a small percentage (<15%) of the time. The system appeared to be nitrate-depleted with surface water concentrations averaging 1.3 μmol L–1. Increased currents were correlated significantly with a decrease in ice thickness and an increase in ice algal chlorophyll a. Furthermore, pennate diatoms dominated the ice algal community abundance with greater contribution within the strait where currents were greatest. These observations all support the existence of a greater nutrient flux to the ice bottom where currents increased towards the center of the tidal strait, resulting in an increase of bottom ice chlorophyll a biomass by 5–7 times relative to that outside of the strait. Therefore, expanding beyond the long identified biological hotspots of open water polynyas, this paper presents the argument for newly identified hotspots in regions of strong sub-ice currents but persistent ice covers, so called “invisible polynyas”.

scholarly journals The Arctic Ocean Multi-Year Ice Balance, 1979-82

1990 ◽  
Vol 14 ◽  
pp. 252-255 ◽  
Author(s):  
D.A. Rothrock ◽  
D.R. Thomas
Keyword(s):  
Arctic Ocean ◽  
Open Water ◽  
Measurement Model ◽  
The Arctic ◽  
First Year ◽  
Independent Data ◽  
Self Consistent ◽  
Buoy Data ◽  
Parameter Values ◽  
Self Consistency

A method of determining the temporally varying “state” of the ice cover (the concentrations of three surface types: open water, first-year ice, and multi-year ice) is presented. The methodology is that of Kalman smoothing: a physical model and a measurement model are used to blend satellite passive microwave data and buoy data to give an optimal estimate of the ice state. The estimates are optimal only to the degree that model parameter values are known and assumptions about variances are met. Uncertainty about these values and assumptions, and lack of independent data with which to compare results,leaves self-consistency as the most important test of results. A four-year record (1979-82) of the estimated Arctic Ocean ice balance is presented and shown to be self-consistent. Results are discussed in terms of the Arctic multi-year ice balance, which may be an important factor in the interaction ofocean, sea ice and climate because of its relationship to the minimum summer ice extent. The estimated area of multi-year ice decreases each year, but the decrease is small and insignificant based on four years of results. Furthermore, the observed decrease may be due to instrument drift or changes in the multi-year ice signature.

scholarly journals Production of Chromophoric Dissolved Organic Matter (CDOM) in Laboratory Cultures of Arctic Sea Ice Algae

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 926
Author(s):  
Guiju Li ◽  
Huixiang Xie ◽  
Guisheng Song ◽  
Michel Gosselin
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Sea Ice ◽  
Chlorophyll A ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Chromophoric Dissolved Organic Matter ◽  
Ice Algae ◽  
Production Rates ◽  
Arctic Sea

Chromophoric dissolved organic matter (CDOM) is highly enriched in bottom sea ice in the Arctic during ice algal blooms, giving rise to multifaceted ecological implications in both the sea ice and the underlying seawater. We conducted laboratory culture incubations to assess the potential role of ice algae in the accumulation of CDOM in Arctic sea ice. Non-axenic monocultures of Attheya septentrionalis and Nitzschia frigida and a natural ice algal assemblage (NIAA) were grown at 4 °C in an f/2 medium under cool white fluorescent light. Culture samples were collected several days apart throughout the exponential, stationary, and senescent phases, and analyzed for CDOM absorbance, chlorophyll a, and bacterial cell abundance. The cultures displayed apparent specific growth rates of algal and bacterial cells comparable to those in the field. Accumulations of CDOM were observed in all cultures during the time-course incubations, with the senescent phase showing the largest accumulations and the highest production rates. The senescent-phase production rate for NIAA was ~40% higher than that for A. septentrionalis. The chlorophyll a-normalized CDOM production rates in the cultures are comparable to those reported for Arctic first-year sea ice. The absorption spectra of CDOM in the cultures exhibited characteristic short-ultraviolet shoulders similar to those previously identified in sea ice. This study demonstrates that ice algal-derived CDOM can account for the springtime accumulation of CDOM in Arctic sea ice.

scholarly journals MYI Floes Identification Based on the Texture and Shape Feature from Dual-Polarized Sentinel-1 Imagery

2020 ◽  
Vol 12 (19) ◽  
pp. 3221
Author(s):  
Shiyi Chen ◽  
Mohammed Shokr ◽  
Xinqing Li ◽  
Yufang Ye ◽  
Zhilun Zhang ◽  
...  
Keyword(s):  
Visual Analysis ◽  
Open Water ◽  
New Method ◽  
The Arctic ◽  
First Year ◽  
Ancillary Data ◽  
Sar Images ◽  
Morphological Image Processing ◽  
Automated Algorithms ◽  
Fine Resolution

The Northwest Passage (NWP) in the Arctic is usually covered with hazardous multi-year ice (MYI) and seasonal first-year ice (FYI) in winter, with possible thin ice and open-water areas during transition seasons. Ice classification is important for both marine navigation and climate change studies. Satellite-based Synthetic Aperture Radar (SAR) systems have shown advantages of retrieving this information. Operational ice mapping relies on visual analysis of SAR images along with ancillary data. However, these maps estimate ice types and concentrations within large-size polygons of a few tens or hundreds of kilometers, which are subjectively identified and selected by analysts. This study aims at developing an automated algorithm to identify individual MYI floes from SAR images then classify the rest of the image as FYI and other ice types. The algorithm identifies the MYI floes using extended-maximum operator, morphological image processing, and a few geometrical features. Classifying the rest of the image uses texture and neural network model. The input data is a set of Sentinel-1 A/B Extended Wide (EW) mode images, acquired between September and March 2016–2019. Although the overall accuracy (for all type classification) from the new method scored 93.26%, the accuracy from using the texture classifier only was 75.81%. The kappa coefficient from the former was higher than the latter by 0.25. Compared with the operational ice charts from the Canadian Ice Service, ice type maps from the new method show better distribution of MYI at the fine scale of individual floes. Comparison against MYI concentration from two automated algorithms that use a combination of coarse-resolution passive and active microwave data also confirms the advantage of resolving MYI floes from the fine-resolution SAR.

scholarly journals Regional melt-pond fraction and albedo of thin Arctic first-year drift ice in late summer

2015 ◽  
Vol 9 (1) ◽  
pp. 255-268 ◽  
Author(s):  
D. V. Divine ◽  
M. A. Granskog ◽  
S. R. Hudson ◽  
C. A. Pedersen ◽  
T. I. Karlsen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Surface Type ◽  
Melt Pond ◽  
Melt Ponds

Abstract. The paper presents a case study of the regional (≈150 km) morphological and optical properties of a relatively thin, 70–90 cm modal thickness, first-year Arctic sea ice pack in an advanced stage of melt. The study combines in situ broadband albedo measurements representative of the four main surface types (bare ice, dark melt ponds, bright melt ponds and open water) and images acquired by a helicopter-borne camera system during ice-survey flights. The data were collected during the 8-day ICE12 drift experiment carried out by the Norwegian Polar Institute in the Arctic, north of Svalbard at 82.3° N, from 26 July to 3 August 2012. A set of > 10 000 classified images covering about 28 km2 revealed a homogeneous melt across the study area with melt-pond coverage of ≈ 0.29 and open-water fraction of ≈ 0.11. A decrease in pond fractions observed in the 30 km marginal ice zone (MIZ) occurred in parallel with an increase in open-water coverage. The moving block bootstrap technique applied to sequences of classified sea-ice images and albedo of the four surface types yielded a regional albedo estimate of 0.37 (0.35; 0.40) and regional sea-ice albedo of 0.44 (0.42; 0.46). Random sampling from the set of classified images allowed assessment of the aggregate scale of at least 0.7 km2 for the study area. For the current setup configuration it implies a minimum set of 300 images to process in order to gain adequate statistics on the state of the ice cover. Variance analysis also emphasized the importance of longer series of in situ albedo measurements conducted for each surface type when performing regional upscaling. The uncertainty in the mean estimates of surface type albedo from in situ measurements contributed up to 95% of the variance of the estimated regional albedo, with the remaining variance resulting from the spatial inhomogeneity of sea-ice cover.

The Thinning of Arctic Sea Ice, 1988–2003: Have We Passed a Tipping Point?

2005 ◽  
Vol 18 (22) ◽  
pp. 4879-4894 ◽  
Author(s):  
R. W. Lindsay ◽  
J. Zhang
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Ocean Model ◽  
Tipping Point ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Positive Feedbacks ◽  
Cooling Period ◽  
Arctic Sea

Abstract Recent observations of summer Arctic sea ice over the satellite era show that record or near-record lows for the ice extent occurred in the years 2002–05. To determine the physical processes contributing to these changes in the Arctic pack ice, model results from a regional coupled ice–ocean model have been analyzed. Since 1988 the thickness of the simulated basinwide ice thinned by 1.31 m or 43%. The thinning is greatest along the coast in the sector from the Chukchi Sea to the Beaufort Sea to Greenland. It is hypothesized that the thinning since 1988 is due to preconditioning, a trigger, and positive feedbacks: 1) the fall, winter, and spring air temperatures over the Arctic Ocean have gradually increased over the last 50 yr, leading to reduced thickness of first-year ice at the start of summer; 2) a temporary shift, starting in 1989, of two principal climate indexes (the Arctic Oscillation and Pacific Decadal Oscillation) caused a flushing of some of the older, thicker ice out of the basin and an increase in the summer open water extent; and 3) the increasing amounts of summer open water allow for increasing absorption of solar radiation, which melts the ice, warms the water, and promotes creation of thinner first-year ice, ice that often entirely melts by the end of the subsequent summer. Internal thermodynamic changes related to the positive ice–albedo feedback, not external forcing, dominate the thinning processes over the last 16 yr. This feedback continues to drive the thinning after the climate indexes return to near-normal conditions in the late 1990s. The late 1980s and early 1990s could be considered a tipping point during which the ice–ocean system began to enter a new era of thinning ice and increasing summer open water because of positive feedbacks. It remains to be seen if this era will persist or if a sustained cooling period can reverse the processes.

scholarly journals Sea ice biota: Excerpts from the State of the Arctic Marine Biodiversity Report by the Sea Ice Biota Expert Network/CBMP

2018 ◽  
Author(s):  
Haakon Hop ◽  
Bodil A. Bluhm ◽  
Igor A. Melnikov ◽  
Michel Poulin ◽  
Mikko Vihtakari ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Arctic Sea Ice ◽  
Algal Community ◽  
The Arctic ◽  
Marine Biodiversity ◽  
Cascading Effects ◽  
Marine Areas ◽  
Monitoring Protocols ◽  
Expert Network

Sea ice is an important Arctic habitat that supports a high diversity of species—with over 1276 protist taxa alone. Multi-year sea ice is being replaced by first-year ice and open water, which will cause shifts in ice algal communities with cascading effects on the ice-associated ecosystem. Documentation of ice biota composition, abundance and natural variability is critical for evaluating responses to the decline in Arctic sea ice. The Sea-ice Biota Expert Network, therefore, aggregated and reviewed data on status and trends of ice-associated Bacteria, Archaea, microalgae, meiofauna, and under-ice macrofauna Focal Ecosystem Components (FECs) across eight Arctic Marine Areas as well as current monitoring. Sea ice biota monitoring has occurred most frequently in the central Arctic, Svalbard area, Barrow (Alaska) and the Canadian Arctic, with recent sites in northern Greenland. Sea ice algal community structure has possibly changed in the central Arctic between the 1980s and 2010s, and ice-amphipod abundance and biomass have declined in the Svalbard area since the 1980s. Consistent monitoring protocols, equipment and methodology should be implemented. The presentation also evaluates dominant drivers of observed trends, and knowledge and monitoring gaps.

scholarly journals Sea ice biota: Excerpts from the State of the Arctic Marine Biodiversity Report by the Sea Ice Biota Expert Network/CBMP

2018 ◽  
Author(s):  
Haakon Hop ◽  
Bodil A. Bluhm ◽  
Igor A. Melnikov ◽  
Michel Poulin ◽  
Mikko Vihtakari ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Arctic Sea Ice ◽  
Algal Community ◽  
The Arctic ◽  
Marine Biodiversity ◽  
Cascading Effects ◽  
Marine Areas ◽  
Monitoring Protocols ◽  
Expert Network

Sea ice is an important Arctic habitat that supports a high diversity of species—with over 1276 protist taxa alone. Multi-year sea ice is being replaced by first-year ice and open water, which will cause shifts in ice algal communities with cascading effects on the ice-associated ecosystem. Documentation of ice biota composition, abundance and natural variability is critical for evaluating responses to the decline in Arctic sea ice. The Sea-ice Biota Expert Network, therefore, aggregated and reviewed data on status and trends of ice-associated Bacteria, Archaea, microalgae, meiofauna, and under-ice macrofauna Focal Ecosystem Components (FECs) across eight Arctic Marine Areas as well as current monitoring. Sea ice biota monitoring has occurred most frequently in the central Arctic, Svalbard area, Barrow (Alaska) and the Canadian Arctic, with recent sites in northern Greenland. Sea ice algal community structure has possibly changed in the central Arctic between the 1980s and 2010s, and ice-amphipod abundance and biomass have declined in the Svalbard area since the 1980s. Consistent monitoring protocols, equipment and methodology should be implemented. The presentation also evaluates dominant drivers of observed trends, and knowledge and monitoring gaps.

scholarly journals The Arctic Ocean Multi-Year Ice Balance, 1979-82

1990 ◽  
Vol 14 ◽  
pp. 252-255 ◽  
Author(s):  
D.A. Rothrock ◽  
D.R. Thomas
Keyword(s):  
Arctic Ocean ◽  
Open Water ◽  
Measurement Model ◽  
The Arctic ◽  
First Year ◽  
Independent Data ◽  
Self Consistent ◽  
Buoy Data ◽  
Parameter Values ◽  
Self Consistency

A method of determining the temporally varying “state” of the ice cover (the concentrations of three surface types: open water, first-year ice, and multi-year ice) is presented. The methodology is that of Kalman smoothing: a physical model and a measurement model are used to blend satellite passive microwave data and buoy data to give an optimal estimate of the ice state. The estimates are optimal only to the degree that model parameter values are known and assumptions about variances are met. Uncertainty about these values and assumptions, and lack of independent data with which to compare results,leaves self-consistency as the most important test of results. A four-year record (1979-82) of the estimated Arctic Ocean ice balance is presented and shown to be self-consistent. Results are discussed in terms of the Arctic multi-year ice balance, which may be an important factor in the interaction ofocean, sea ice and climate because of its relationship to the minimum summer ice extent. The estimated area of multi-year ice decreases each year, but the decrease is small and insignificant based on four years of results. Furthermore, the observed decrease may be due to instrument drift or changes in the multi-year ice signature.

scholarly journals Regional albedo of Arctic first-year drift ice in advanced stages of melt from the combination of in situ measurements and aerial imagery

2014 ◽  
Vol 8 (4) ◽  
pp. 3699-3732
Author(s):  
D. V. Divine ◽  
M. A. Granskog ◽  
S. R. Hudson ◽  
C. A. Pedersen ◽  
T. I. Karlsen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
In Situ Measurements ◽  
Arctic Sea Ice ◽  
Aerial Imagery ◽  
The Arctic ◽  
First Year ◽  
Melt Ponds ◽  
Advanced Stages

Abstract. The paper presents a case study of the regional (≈ 150 km) broadband albedo of first year Arctic sea ice in advanced stages of melt, estimated from a combination of in situ albedo measurements and aerial imagery. The data were collected during the eight day ICE12 drift experiment carried out by the Norwegian Polar Institute in the Arctic north of Svalbard at 82.3° N from 26 July to 3 August 2012. The study uses in situ albedo measurements representative of the four main surface types: bare ice, dark melt ponds, bright melt ponds and open water. Images acquired by a helicopter borne camera system during ice survey flights covered about 28 km2. A subset of > 8000 images from the area of homogeneous melt with open water fraction of ≈ 0.11 and melt pond coverage of ≈ 0.25 used in the upscaling yielded a regional albedo estimate of 0.40 (0.38; 0.42). The 95% confidence interval on the estimate was derived using the moving block bootstrap approach applied to sequences of classified sea ice images and albedo of the four surface types treated as random variables. Uncertainty in the mean estimates of surface type albedo from in situ measurements contributed some 95% of the variance of the estimated regional albedo, with the remaining variance resulting from the spatial inhomogeneity of sea ice cover. The results of the study are of relevance for the modeling of sea ice processes in climate simulations. It particularly concerns the period of summer melt, when the optical properties of sea ice undergo substantial changes, which existing sea ice models have significant diffuculty accurately reproducing.

POLAR LOW DETECTION USING SOLAB SIOWS ARCTIC PORTAL

2017 ◽  
Author(s):  
Olga Mashtaler ◽  
Olga Mashtaler ◽  
Alexander Myasoedov ◽  
Alexander Myasoedov ◽  
Elizaveta Zabolotskikh ◽  
...  
Keyword(s):  
Model Development ◽  
Sharp Decrease ◽  
Open Water ◽  
The Arctic ◽  
Wind Fields ◽  
Polar Lows ◽  
Statistical Regularities ◽  
Meteorological Observations ◽  
Strong Winds ◽  
Synthetic Aperture Radars

The relevance of the polar lows (PLs) research is justified by their great destructive power and creation of threat to the safety of navigation in the high latitudes and along the Northern Sea Route. The most dangerous effects on maritime activities are strong winds, waves and icing. In addition, the study of the PLs acquires relevance due to the sharp decrease of the sea ice area in the Arctic in recent years and the emergence of areas of open water, suitable for the appearance and development of PLs. However, despite the importance of PLs, they are apparently not sufficiently studied. As there are no meteorological observations in the areas of their appearance, the main source of information about them are satellite observations. By using images on the SOLab SIOWS Arctic Portal from multiple satellites operating in the IR and visible ranges (e.g., MODIS and AVHRR), and using near-water wind fields from high resolution synthetic aperture radars (Sentine-1, ASAR) and low resolution scatterometers (ASCAT), we identify polar lows in various parts of the Arctic, revealing statistical regularities in the appearance of PLs, their distribution and intensity. Collected database of Pls and their characteristics will be used for further PLs forecasting model development.

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