Sea Ice Phenology Research Articles

Seasonal Sea Ice Conditions Affect Caribou Crossing Areas Around Qikiqtaq, Nunavut: Uqsuqtuurmiut Knowledge Guides Ice Chart Analysis

Though polar ecologists consider sea ice primarily as a habitat for marine mammals, caribou use sea ice to complete their reproductive cycles, to access areas with preferred climatic and vegetation conditions, and to avoid predators seasonally and sporadically. Building on previous caribou research in Uqsuqtuuq (Gjoa Haven, Nunavut), we explored the connections between caribou and sea ice phenology in 5 community-identified caribou crossing areas around Qikiqtaq (King William Island). We defined freeze-up and breakup based on Uqsuqtuurmiut (people of Uqsuqtuuq) knowledge of caribou habitat requirements, to orient our analysis to the complex and multifaceted hazards that caribou can encounter while moving through their dynamic and unpredictable sea ice habitat. We investigated the reliability of caribou sea ice habitat surrounding Qikiqtaq, prioritizing key transitional periods with intensified caribou movement. We use regional ice charts produced by the Canadian Ice Service (CIS) and held workshops with Uqsuqtuurmiut to understand how sea ice phenology and caribou mobility have changed over time. The high spatial and temporal variability of sea ice phenology around Qikiqtaq facilitates caribou moving across sea ice should they need to respond to seasonal or unpredictable changes in ecological conditions or anthropogenic disturbance. Therefore, these localized sea ice conditions may increase caribou resiliency to changes or extreme events by providing alternative options for movement across the sea ice. We encourage others to consider the needs of wildlife sea ice users when assessing or providing ice information.

Heightened heart rate but similar flight responses to evolved versus recent predators in an Arctic seabird

Predator-prey dynamics in the Arctic are being altered with changing sea ice phenology. The increasing frequency of predation on colonial nesting seabirds and their eggs by the polar bear (<em>Ursus maritimus</em>) is a consequence of bears shifting to terrestrial food resources through a shortened seal-hunting season. We examined antipredator responses in a colony of nesting Common Eiders (<em>Somateria mollissima</em>) on East Bay Island, Nunavut, Canada, which is exposed to established nest predators, such as arctic fox (<em>Vulpes lagopus</em>), but also to recent increases in polar bear nest predation due to the bears’ lost on-ice hunting opportunities. Given eiders’ limited eco-evolutionary experience with bears, we aimed to experimentally contrast eider responses to the recent predation pressure by polar bears to those induced by their more traditional mammalian predator, the arctic fox. Our goal was to characterize whether this population of eiders was vulnerable to a changing predator regime. Using simulated approaches of visual stimuli of both predator types, we measured eider heart rate and flight initiation distance as physiological and behavioral metrics, respectively, to characterize the perceived risk of and subsequent response to imminent threat posed by these two predators that differ in historical encounter rates. Eider heart rates were more responsive to impending visual cues of arctic foxes compared to polar bears, but birds responded behaviorally to all simulated threats with similar flight initiation distances. Results suggest eiders may not perceive the full risk that bears pose as egg and adult predators, and are therefore expected to suffer negative fitness consequences from this ongoing and increasing interaction. Eiders may therefore require conservation intervention to aid in their management.

Arctic summer sea ice phenology including ponding from 1982 to 2017

Arctic summer sea ice phenology including ponding from 1982 to 2017

Sea ice phenology in the Caspian Sea

To understand the spatial and temporal variations in the extent and timing of sea ice in the Caspian Sea (CS), 15 years of sea ice presence and its phenology (freeze-up, break-up, and duration) were studied in the Northern CS (NCS) for a period from 2004 to 2018. This study indicated that the percentage of sea ice covered area in the CS showed fluctuations ranging from 54.2% in 2004 to more than 89% in 2006 and 2008. This study, furthermore, found regional differences within the NCS in sea ice phonological features during 2004 to 2018. Specifically, earlier sea ice formation, later ice melt, and longer ice periods were observed in the eastern than the western NCS. Noticeable interannual changes were also observed in the timing and duration of the NCS ice (2004-2018). However, most parts of the NCS did not show significant trends (P&gt;0.05) in the formation, decay, and duration of sea ice and their interannual variability. The observed spatial and temporal patterns in the CS ice can have implications for phytoplankton blooms and higher trophic levels, such as fish and endangered Caspian seal populations and merits further investigation.

The stress of Arctic warming on polar bears.

Arctic ecosystems are changing rapidly in response to climate warming. While Arctic mammals are highly evolved to these extreme environments, particularly with respect to their stress axis, some species may have limited capacity to adapt to this change. We examined changes in key components of the stress axis (cortisol and its carrier protein-corticosteroid binding globulin [CBG]) in polar bears (Ursus maritimus) from western Hudson Bay (N=300) over a 33year period (1983-2015) during which time the ice-free period was increasing. Changing sea ice phenology limits spring hunting opportunities and extends the period of onshore fasting. We assessed the response of polar bears to a standardized stressor (helicopter pursuit, darting, and immobilization) during their onshore fasting period (late summer-autumn) and quantified the serum levels of the maximum corticosteroid binding capacity (MCBC) of CBG, the serum protein that binds cortisol strongly, and free cortisol (FC). We quantified bear condition (age, sex, female with cubs or not, fat condition), sea ice (breakup in spring-summer, 1year lagged freeze-up in autumn), and duration of fasting until sample collection as well as cumulative impacts of the latter environmental traits from the previous year. Data were separated into "good" years (1983-1990) when conditions were thought to be optimal and "poor" years (1991-2015) when sea ice conditions deteriorated and fasting on land was extended. MCBC explained 39.4% of the variation in the good years, but only 28.1% in the poor ones, using both biological and environmental variables. MCBC levels decreased with age. Changes in FC were complex, but more poorly explained. Counterintuitively, MCBC levels increased with increased time onshore, 1year lag effects, and in poor ice years. We conclude that MCBC is a biomarker of stress in polar bears and that the changes we document are a consequence of climate warming.

Space-use strategy affects energy requirements in Barents Sea polar bears

Polar bearsUrsus maritimusare currently facing rapid environmental changes with loss of sea ice and shifts in their prey distribution. Two distinct ecotypes exist in the Barents Sea, where sea ice is decreasing at the highest rate in the Arctic. Coastal bears remain within the Archipelago of Svalbard year-round, whereas offshore bears follow the marginal ice zone (MIZ). We explored these 2 ecotypes’ habitat use, activity and energy needs as well as seasonal variation within these parameters. During the period from 2011-2018, adult female polar bears were equipped with GPS collars and activity sensors (n = 84); 46 of these were equipped with conductivity switches to record aquatic behaviour. Offshore bears travelled longer distances at a higher speed on land and at sea away from land and had a higher activity rate compared to coastal bears. This translated into higher overall energy expenditure. Offshore bears also undertook more distant and energetically costly trips from land to the MIZ, swimming in open water. Both ecotypes showed similar seasonal patterns of activity and movement consistent with their life history linked to sea ice phenology. Despite higher energy expenditure, the offshore strategy seemed to be as profitable as the coastal one as females had marginally better spring body condition, likely due to their specialized high caloric diet of seals throughout the year. However, both ecotypes are currently experiencing habitat changes. Future studies should aim to predict how rapidly declining sea ice in the Barents Sea may challenge polar bears energetically during the coming decades.

Biological and geochemical changes in shallow lakes of the Hudson Bay Lowlands: a response to recent warming

The Hudson Bay Lowlands (HBL) region of the far north of Ontario (Canada) is expected to undergo considerable physical, chemical and biological change as a result of ongoing climatic change. Previous research in the region has shown marked limnological changes during the past ~ 20 years in relatively deep lakes that have been attributed to increased air temperatures and changes in sea ice phenology in Hudson Bay since the mid-1990s. Here, we present diatom assemblage, primary production and geochemical data from lake sediments documenting recent limnological change in two shallow sub-arctic lakes in the Sutton River region of the HBL. Both lakes recorded increased whole-lake production and diatom diversity changes that are consistent with a longer ice-free period and growing season. Changes in diatom composition at Wolfgang Lake were characterized by a response amongst benthic/periphytic taxa whereas a modest increase in planktonic diatoms was observed at Sam Lake. Geochemical changes (δ15N, C/N and %N) were temporally coherent with diatom assemblage changes, but showed different responses in the two study lakes. Thus, although the biological and geochemical changes were consistent with recent warming, differences in the nature and timing of these shifts illustrate the heterogeneous nature of shallow lakes, and suggest that local (catchment-specific) factors are important determinants of the trajectory of limnological change in these sensitive systems.

Identifying shifts in maternity den phenology and habitat characteristics of polar bears (Ursus maritimus) in Baffin Bay and Kane Basin

The phenology and habitat selection of polar bear (Ursus maritimus) maternity dens may shift over time in response to changing environmental conditions. We compared maternity den phenology and habitat characteristics using satellite telemetry data from adult female polar bears from the Baffin Bay (BB) (n = 16 dens; 2009–2015) and Kane Basin (KB) subpopulations (n = 3 dens; 2012–2015) to previously published maternity den data from 1991 to 1997 (BB n = 8 dens; KB n = 3 dens). BB maternity denning duration decreased from a mean of 194.1 days (SD = 21.0 days, n = 8) in the 1990s, to a mean of 167.1 days (SD = 27.6 days, n = 16; p = 0.017) in the 2000s. Delayed den entry accounted for shorter denning durations (1990s entry date $$\bar{x}$$ = 7 September; 2000s entry date $$\bar{x}$$ = 5 October; p = 0.018). For dens habitat characteristics of which could be measured, BB maternity dens in the 2000s occurred at higher elevations ( $$\bar{x}$$ = 707.0 m, SD = 284.9 m, n = 15; p = 0.003) and greater slopes ( $$\bar{x}$$ = 23.1°, SD = 7.4°; p = 0.003) than the 1990s (elevation $$\bar{x}$$ ± SD = 351.3 ± 194.5 m, n = 8; slope $$\bar{x}$$ ± SD = 11.9 ± 6.4°). Aspect also significantly differed between the 1990s ( $$\bar{x}$$ = 51.3°) and 2000s BB maternity dens ( $$\bar{x}$$ = 199.7°; Watson’s U 2 p = 0.042). KB dens were not statistically compared due to low sample size (n = 3 dens in both periods). Shifts in sea ice phenology and snow availability may explain the observed changes.

Sea ice phenology and primary productivity pulses shape breeding success in Arctic seabirds

Spring sea ice phenology regulates the timing of the two consecutive pulses of marine autotrophs that form the base of the Arctic marine food webs. This timing has been suggested to be the single most essential driver of secondary production and the efficiency with which biomass and energy are transferred to higher trophic levels. We investigated the chronological sequence of productivity pulses and its potential cascading impacts on the reproductive performance of the High Arctic seabird community from Svalbard, Norway. We provide evidence that interannual changes in the seasonal patterns of marine productivity may impact the breeding performance of little auks and Brünnich’s guillemots. These results may be of particular interest given that current global warming trends in the Barents Sea region predict one of the highest rates of sea ice loss within the circumpolar Arctic. However, local- to regional-scale heterogeneity in sea ice melting phenology may add uncertainty to predictions of climate-driven environmental impacts on seabirds. Indeed, our fine-scale analysis reveals that the inshore Brünnich’s guillemots are facing a slower advancement in the timing of ice melt compared to the offshore-foraging little auks. We provide a suitable framework for analyzing the effects of climate-driven sea ice disappearance on seabird fitness.

Circumpolar analysis of the Adélie Penguin reveals the importance of environmental variability in phenological mismatch.

Evidence of climate-change-driven shifts in plant and animal phenology have raised concerns that certain trophic interactions may be increasingly mismatched in time, resulting in declines in reproductive success. Given the constraints imposed by extreme seasonality at high latitudes and the rapid shifts in phenology seen in the Arctic, we would also expect Antarctic species to be highly vulnerable to climate-change-driven phenological mismatches with their environment. However, few studies have assessed the impacts of phenological change in Antarctica. Using the largest database of phytoplankton phenology, sea-ice phenology, and Adélie Penguin breeding phenology and breeding success assembled to date, we find that, while a temporal match between Penguin breeding phenology and optimal environmental conditions sets an upper limit on breeding success, only a weak relationship to the mean exists. Despite previous work suggesting that divergent trends in Adélie Penguin breeding phenology are apparent across the Antarctic continent, we find no such trends. Furthermore, we find no trend in the magnitude of phenological mismatch, suggesting that mismatch is driven by interannual variability in environmental conditions rather than climate-change-driven trends, as observed in other systems. We propose several criteria necessary for a species to experience a strong climate-change-driven phenological mismatch, of which several may be violated by this system.

Influence of sea ice phenology on the movement ecology of ringed seals across their latitudinal range

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 562:237-250 (2016) - DOI: https://doi.org/10.3354/meps11950 Influence of sea ice phenology on the movement ecology of ringed seals across their latitudinal range David J. Yurkowski1,*, Christina A. D. Semeniuk1, Lois A. Harwood2, Aqqalu Rosing-Asvid3, Rune Dietz4, Tanya M. Brown5, Sydney Clackett1, Alice Grgicak-Mannion1, Aaron T. Fisk1, Steven H. Ferguson6 1Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada 2Department of Fisheries and Oceans, 301-5204 50th Avenue, Yellowknife, Northwest Territories X1A 1E2, Canada 3Greenland Institute of Natural Resources, Kivioq 2, PO Box 570, 3900 Nuuk, Greenland 4Department of Bioscience, Aarhus University, Arctic Research Centre, Frederiksborgvej 399, 4000 Roskilde, Denmark 5Department of Geography, Memorial University of Newfoundland, 230 Elizabeth Ave., St. John’s, Newfoundland A1B 3X9, Canada 6Freshwater Institute, Department of Fisheries and Oceans, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada *Corresponding author: dyurkowski1@gmail.com ABSTRACT: Environmental variation influences resource distribution, thereby affecting animal movement and foraging decisions. Climate change is altering environmental processes worldwide, but particularly in the Arctic, where changes in the phenology of sea ice have been redistributing resources across space and time. How polar marine predators such as ringed seals Pusa hispida hispida, whose ecology is tightly tied to sea ice, respond to different sea ice dynamics across large spatial scales is generally unknown. Here, behavioural states (resident and traveling) were estimated using state-space models on adult (n = 45) and subadult (n = 85) ringed seal satellite telemetry tracks from 6 Arctic locations. Tagged ringed seals spanned a wide latitudinal (56.54° to 75.58°N) and sea ice phenological range from short (1 to 2 mo) to longer (6 mo) ice-free periods. We assessed the influences of age class and several intra- and inter-annual environmental variables on ringed seal movement ecology. Both adults and subadults spent most of the ice-free season in a resident state (93 and 77%, respectively). A latitudinal gradient was characterised, where longer ice-free seasons and less inter-annual variability in sea ice phenology at lower latitudes were related to ringed seals spending more time in a resident state than their conspecifics at higher latitudes (90 versus 58%, respectively), where the ice-free season was shorter and sea ice phenology between years was less synchronous. Ringed seals are responding to latitudinal differences in sea ice phenology which affect prey distribution, suggesting plasticity in their foraging decisions and spatiotemporal differences in prey distribution across the rapidly changing Arctic. KEY WORDS: Animal movement · Spatial ecology · Arctic · Foraging behaviour · Climate change · Marine mammal Full text in pdf format Supplementary material PreviousNextCite this article as: Yurkowski DJ, Semeniuk CAD, Harwood LA, Rosing-Asvid A and others (2016) Influence of sea ice phenology on the movement ecology of ringed seals across their latitudinal range. Mar Ecol Prog Ser 562:237-250. https://doi.org/10.3354/meps11950 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 562. Online publication date: December 29, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Mass Loss Rates of Fasting Polar Bears.

Polar bears (Ursus maritimus) have adapted to an annual cyclic regime of feeding and fasting, which is extreme in seasonal sea ice regions of the Arctic. As a consequence of climate change, sea ice breakup has become earlier and the duration of the open-water period through which polar bears must rely on fat reserves has increased. To date, there is limited empirical data with which to evaluate the potential energetic capacity of polar bears to withstand longer fasts. We measured the incoming and outgoing mass of inactive polar bears (n = 142) that were temporarily detained by Manitoba Conservation and Water Stewardship during the open-water period near the town of Churchill, Manitoba, Canada, in 2009-2014. Polar bears were given access to water but not food and held for a median length of 17 d. Median mass loss rates were 1.0 kg/d, while median mass-specific loss rates were 0.5%/d, similar to other species with high adiposity and prolonged fasting capacities. Mass loss by unfed captive adult males was identical to that lost by free-ranging individuals, suggesting that terrestrial feeding contributes little to offset mass loss. The inferred metabolic rate was comparable to a basal mammalian rate, suggesting that while on land, polar bears can maintain a depressed metabolic rate to conserve energy. Finally, we estimated time to starvation for subadults and adult males for the on-land period. Results suggest that at 180 d of fasting, 56%-63% of subadults and 18%-24% of adult males in this study would die of starvation. Results corroborate previous assessments on the limits of polar bear capacity to withstand lengthening ice-free seasons and emphasize the greater sensitivity of subadults to changes in sea ice phenology.

Assessing stress in Western Hudson Bay polar bears using hair cortisol concentration as a biomarker

The development of novel biomarkers to help assess whether polar bear (Ursus maritimus) health is impacted by long-term physiological stress associated with climate change represents an emerging area of research. Reductions in sea ice cover and food availability are potentially stressful, and chronic stress can have deleterious effects that may impair individual and population level health. Cortisol is the principal effector hormone of the stress response and has previously been linked to aspects of polar bear life history (e.g., reproduction and growth) known to be negatively influenced by environmental change. Understanding stress is important for polar bears at the southern limit of their range, such as those in Western Hudson Bay (WH), where rapidly changing sea ice phenology threatens population viability. We examined the relationships between age, reproductive status, and body condition (fatness) and hair cortisol concentration (HCC) in 729 polar bear hair samples collected in WH from 2004–2013. Overall, there was a negative relationship between fatness and HCC, suggesting that bears in poorer body condition experienced higher levels of stress. However, when reproductive status was included in our analysis, this relationship only held for male and lone female bears. Females with dependent offspring had consistently low fatness and elevated HCC, likely because of the high cost of maternal care. We also found a positive correlation between HCC and age for: (1) bears in poor body condition, possibly due to nutritional stress compounding effects of aging; and (2) male bears, potentially due to stress and injury associated with intrasexual mate competition. These findings support the use of HCC as a biomarker for polar bear health. Furthermore, we have established a HCC benchmark against which future population-level effects of climate change in WH polar bears can be compared.

Rapid Environmental Change Drives Increased Land Use by an Arctic Marine Predator.

In the Arctic Ocean’s southern Beaufort Sea (SB), the length of the sea ice melt season (i.e., period between the onset of sea ice break-up in summer and freeze-up in fall) has increased substantially since the late 1990s. Historically, polar bears (Ursus maritimus) of the SB have mostly remained on the sea ice year-round (except for those that came ashore to den), but recent changes in the extent and phenology of sea ice habitat have coincided with evidence that use of terrestrial habitat is increasing. We characterized the spatial behavior of polar bears spending summer and fall on land along Alaska’s north coast to better understand the nexus between rapid environmental change and increased use of terrestrial habitat. We found that the percentage of radiocollared adult females from the SB subpopulation coming ashore has tripled over 15 years. Moreover, we detected trends of earlier arrival on shore, increased length of stay, and later departure back to sea ice, all of which were related to declines in the availability of sea ice habitat over the continental shelf and changes to sea ice phenology. Since the late 1990s, the mean duration of the open-water season in the SB increased by 36 days, and the mean length of stay on shore increased by 31 days. While on shore, the distribution of polar bears was influenced by the availability of scavenge subsidies in the form of subsistence-harvested bowhead whale (Balaena mysticetus) remains aggregated at sites along the coast. The declining spatio-temporal availability of sea ice habitat and increased availability of human-provisioned resources are likely to result in increased use of land. Increased residency on land is cause for concern given that, while there, bears may be exposed to a greater array of risk factors including those associated with increased human activities.

Summer and winter whales in the Pacific Arctic

Changes in sea ice phenology have been profound in the Pacific Arctic, where the seasonal open-water period has increased by ~1.5 months over the past 30 years. The greatest changes in the open water season have occurred in fall resulting in changes to the Arctic ecosystem, including increased primary productivity, changing food web structure, and opening of new habitat. In the “new normal” Arctic, sub-arctic “summer” whales (fin, humpback, and killer) are poised to inhabit new seasonally ice-free habitats in the Arctic. The spatial and seasonal occurrence of summer and “winter” (bowhead) whales over 5 years from September through December was examined by deploying hydrophones in Bering Strait and comparing acoustic occurrence of the species concomitant with decadal-scale changes in seasonal sea ice. Fin and humpback whale acoustic detections extended from summer to late autumn while killer whale detections were more sporadic. Inter-annual differences in acoustic detections appear to be driven by interannual differences in the environment. Bowhead whale detections generally began after the departure of the summer whales and continued through the winter. In a future with further seasonal sea ice reductions, however, increased competition for resources between sub-Arctic and Arctic species may arise to the detriment of winter whales.

Monitoring Arctic sea ice phenology change using hypertemporal remotely sensed data: 1989–2010

Arctic sea ice has undergone a significant decline in recent years. Previous studies have demonstrated that the annual sea ice cycle has experienced earlier melt and later freeze up, leading to a significant reduction in minimum sea ice extents and the lengthening of the melting season. The Arctic is being transformed into a regime of widespread seasonal ice with a large loss of old and thick multiyear ice in recent years. However, the sea ice change exhibits considerable interannual and regional variability at different spatial and temporal scales. In this study, we present a new method for hypertemporal sea ice data change detection based on the annual sea ice concentration (SIC) profile for the melt months of each year. A decision tree-based classification is adopted to group pixels with similar annual SIC profiles, and a phenology map of each year is generated for visualization. The phenoregion map visualizes the spatial and temporal configurations of ice melt process for a year. The change detection objective is achieved by comparing the phenoregion number of the same pixel in different years. The algorithm further leads to interpretation of anomalies to obtain change maps at the pixel level. Compared to previous sea ice studies that mainly focused on a particular spatial region and commonly use time period averages, the proposed pixel-based approach has the potential to map sea ice data change both temporally and spatially.

Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century.

Arctic marine mammals (AMMs) are icons of climate change, largely because of their close association with sea ice. However, neither a circumpolar assessment of AMM status nor a standardized metric of sea ice habitat change is available. We summarized available data on abundance and trend for each AMM species and recognized subpopulation. We also examined species diversity, the extent of human use, and temporal trends in sea ice habitat for 12 regions of the Arctic by calculating the dates of spring sea ice retreat and fall sea ice advance from satellite data (1979–2013). Estimates of AMM abundance varied greatly in quality, and few studies were long enough for trend analysis. Of the AMM subpopulations, 78% (61 of 78) are legally harvested for subsistence purposes. Changes in sea ice phenology have been profound. In all regions except the Bering Sea, the duration of the summer (i.e., reduced ice) period increased by 5–10 weeks and by >20 weeks in the Barents Sea between 1979 and 2013. In light of generally poor data, the importance of human use, and forecasted environmental changes in the 21st century, we recommend the following for effective AMM conservation: maintain and improve comanagement by local, federal, and international partners; recognize spatial and temporal variability in AMM subpopulation response to climate change; implement monitoring programs with clear goals; mitigate cumulative impacts of increased human activity; and recognize the limits of current protected species legislation.

Evaluation of the Interactive Multisensor Snow and Ice Mapping System (IMS) for monitoring sea ice phenology

We present an evaluation of the Interactive Multisensor Snow and Ice Mapping System (IMS) for monitoring northern hemisphere sea ice phenology. Analysts utilize a variety of datasets to manually derive the daily extent of snow, ice, water and land, available at both 24 and 4km. The 4km IMS product was assessed for 2004–2008 against several previously established melt/freeze algorithms using Scatterometer Image Reconstruction (SIR) SeaWinds/QuikSCAT (QuikSCAT) backscatter (σ°), Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) brightness temperature (TB) measurements, data from the Special Sensor Microwave/Image data (SSM/I) and sea ice concentrations derived from DMSP Special Sensor Microwave/Imager–Special Sensor Microwave Imager Sounder (SSMI–SSMIS) data (NASATeam dataset). The resolution possible with the 4km IMS product allows for better spatial representation of sea ice along the coastlines, the ice edges and in the narrow channels of the Canadian Arctic Archipelago as compared to the microwave products. IMS detects open water earlier and freeze onset later than the automated microwave products, and also allows for the detection of opening, and the subsequent closing, of leads that the other datasets are unable to detect. Using RADARSAT-1 imagery for evaluation, IMS is shown to outperform the other datasets for the timing and extent of the first open water detection. IMS identified between 17 and 53% greater open water coverage than the other datasets in the narrow channels of the Northwest Passage (Barrow Strait). In order to further the use of IMS for sea ice applications, we derived two new spatial datasets using the full record of IMS data (4km: 2004–present, 24km: 1997–present): melt duration to open water (duration from melt onset detected with SSM/I passive microwave until open water detected by IMS) and first year ice cover duration (duration from freeze onset until open water, both detected by IMS).

Sea ice phenology and timing of primary production pulses in the Arctic Ocean

Arctic organisms are adapted to the strong seasonality of environmental forcing. A small timing mismatch between biological processes and the environment could potentially have significant consequences for the entire food web. Climate warming causes shrinking ice coverage and earlier ice retreat in the Arctic, which is likely to change the timing of primary production. In this study, we test predictions on the interactions among sea ice phenology and production timing of ice algae and pelagic phytoplankton. We do so using the following (1) a synthesis of available satellite observation data; and (2) the application of a coupled ice-ocean ecosystem model. The data and model results suggest that, over a large portion of the Arctic marginal seas, the timing variability in ice retreat at a specific location has a strong impact on the timing variability in pelagic phytoplankton peaks, but weak or no impact on the timing of ice-algae peaks in those regions. The model predicts latitudinal and regional differences in the timing of ice algae biomass peak (varying from April to May) and the time lags between ice algae and pelagic phytoplankton peaks (varying from 45 to 90days). The correlation between the time lag and ice retreat is significant in areas where ice retreat has no significant impact on ice-algae peak timing, suggesting that changes in pelagic phytoplankton peak timing control the variability in time lags. Phenological variability in primary production is likely to have consequences for higher trophic levels, particularly for the zooplankton grazers, whose main food source is composed of the dually pulsed algae production of the Arctic.

Contrasting population changes in sympatric penguin species in association with climate warming

AbstractClimate warming and associated sea ice reductions in Antarctica have modified habitat conditions for some species. These include the congeneric Adélie, chinstrap and gentoo penguins, which now demonstrate remarkable population responses to regional warming. However, inconsistencies in the direction of population changes between species at different study sites complicate the understanding of causal processes. Here, we show that at the South Orkney Islands where the three species breed sympatrically, the less ice‐adapted gentoo penguins increased significantly in numbers over the last 26 years, whereas chinstrap and Adélie penguins both declined. These trends occurred in parallel with regional long‐term warming and significant reduction in sea ice extent. Periodical warm events, with teleconnections to the tropical Pacific, caused cycles in sea ice leading to reduced prey biomass, and simultaneous interannual population decreases in the three penguin species. With the loss of sea ice, Adélie penguins were less buffered against the environment, their numbers fluctuated greatly and their population response was strong and linear. Chinstrap penguins, considered to be better adapted to ice‐free conditions, were affected by discrete events of locally increased ice cover, but showed less variable, nonlinear responses to sea ice loss. Gentoo penguins were temporarily affected by negative anomalies in regional sea ice, but persistent sea ice reductions were likely to increase their available niche, which is likely to be substantially segregated from that of their more abundant congeners. Thus, the regional consequences of global climate perturbations on the sea ice phenology affect the marine ecosystem, with repercussions for penguin food supply and competition for resources. Ultimately, variability in penguin populations with warming reflects the local balance between penguin adaptation to ice conditions and trophic‐mediated changes cascading from global climate forcing.