Sea-Ice Indicators of Polar Bear Habitat

Abstract. Abstract. Nineteen distinct subpopulations of polar bears (Ursus maritimus) are found throughout the Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is tied to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum, or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade−1 in spring, and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days), and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade−1, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of change in marine mammal habitat) were designed to be useful for management agencies. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.

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Sea-ice indicators of polar bear habitat

The Cryosphere ◽

10.5194/tc-10-2027-2016 ◽

2016 ◽

Vol 10 (5) ◽

pp. 2027-2041 ◽

Cited By ~ 61

Author(s):

Harry L. Stern ◽

Kristin L. Laidre

Keyword(s):

Sea Ice ◽

Polar Bear ◽

Barents Sea ◽

Arctic Basin ◽

Concentration Data ◽

Sea Ice Concentration ◽

The Barents Sea ◽

Ice Concentration ◽

Ice Retreat ◽

Sea Ice Retreat

Abstract. Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade−1 in spring and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days) and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade−1, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.

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The Role of Moist Intrusions in Winter Arctic Warming and Sea Ice Decline

Journal of Climate ◽

10.1175/jcli-d-15-0773.1 ◽

2016 ◽

Vol 29 (12) ◽

pp. 4473-4485 ◽

Cited By ~ 122

Author(s):

Cian Woods ◽

Rodrigo Caballero

Keyword(s):

Sea Ice ◽

Barents Sea ◽

Surface Air Temperature ◽

The Arctic ◽

Positive Trend ◽

Sea Ice Concentration ◽

Local Conditions ◽

The Barents Sea ◽

Strong Inversion ◽

Ice Concentration

Abstract This paper examines the trajectories followed by intense intrusions of moist air into the Arctic polar region during autumn and winter and their impact on local temperature and sea ice concentration. It is found that the vertical structure of the warming associated with moist intrusions is bottom amplified, corresponding to a transition of local conditions from a “cold clear” state with a strong inversion to a “warm opaque” state with a weaker inversion. In the marginal sea ice zone of the Barents Sea, the passage of an intrusion also causes a retreat of the ice margin, which persists for many days after the intrusion has passed. The authors find that there is a positive trend in the number of intrusion events crossing 70°N during December and January that can explain roughly 45% of the surface air temperature and 30% of the sea ice concentration trends observed in the Barents Sea during the past two decades.

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Sea ice, temperature, and prey effects on annual variations in mean lengths of a key Arctic fish, Boreogadus saida, in the Barents Sea

ICES Journal of Marine Science ◽

10.1093/icesjms/fsaa040 ◽

2020 ◽

Vol 77 (5) ◽

pp. 1796-1805

Author(s):

Nicolas Dupont ◽

Joël M Durant ◽

Øystein Langangen ◽

Harald Gjøsæter ◽

Leif Christian Stige

Keyword(s):

Sea Ice ◽

Barents Sea ◽

Trophic Levels ◽

The Arctic ◽

Polar Cod ◽

Boreogadus Saida ◽

Sea Ice Concentration ◽

The Barents Sea ◽

Ice Concentration ◽

High Length

Abstract Oceanographic conditions in the Arctic are changing, with sea ice cover decreasing and sea temperatures increasing. Our understanding of the effects on marine populations in the area is, however, limited. Here, we focus on the Barents Sea stock of polar cod (Boreogadus saida). Polar cod is a key fish species for the transfer of energy from zooplankton to higher trophic levels in the Arctic food web. We analyse the relationships between 30-year data series on the length-at-age of polar cod cohorts (ages 0–4) and sea surface temperature, sea ice concentration, prey biomasses, predator indices, and length-at-age the previous year using multiple linear regression. Results for several ages showed that high length-at-age is significantly associated with low sea ice concentration and high length-at-age the previous year. Only length-at-age for age 1 shows a positive significant relationship with prey biomass. Our results suggest that retreating sea ice has positive effects on the growth of polar cod in the Barents Sea despite previous observations of a stagnating stock biomass and decreasing stock abundance. Our results contribute to identifying mechanisms by which climate variability affects the polar cod population, with implications for our understanding of how future climate change may affect Arctic ecosystems.

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Seasonal Trends in Clouds and Radiation over the Arctic Seas from Satellite Observations during 1982 to 2019

Remote Sensing ◽

10.3390/rs13163201 ◽

2021 ◽

Vol 13 (16) ◽

pp. 3201

Author(s):

Xi Wang ◽

Jian Liu ◽

Bingyun Yang ◽

Yansong Bao ◽

George P. Petropoulos ◽

...

Keyword(s):

Sea Ice ◽

Cloud Fraction ◽

Satellite Observations ◽

The Arctic ◽

Arctic Seas ◽

Sea Ice Concentration ◽

Ice Concentration ◽

Ice Retreat ◽

Sea Ice Retreat ◽

Longwave Flux

A long-term dataset of 38 years (1982–2019) from the Advanced Very High Resolution Radiometer (AVHRR) satellite observations is applied to investigate the spatio-temporal seasonal trends in cloud fraction, surface downwelling longwave flux, and surface upwelling longwave flux over the Arctic seas (60~90°N) by the non-parametric methods. The results presented here provide a further contribution to understand the cloud cover and longwave surface radiation trends over the Arctic seas, and their correlations to the shrinking sea ice. Our results suggest that the cloud fraction shows a positive trend for all seasons since 2008. Both surface downwelling and upwelling longwave fluxes present significant positive trends since 1982 with higher magnitudes in autumn and winter. The spatial distribution of the trends is nearly consistent between the cloud fraction and the surface longwave radiation, except for spring over the Chukchi and Beaufort Seas. We further obtained a significant negative correlation between cloud fraction (surface downwelling/upwelling longwave fluxes) and sea-ice concentration during autumn, which is largest in magnitude for regions with substantial sea ice retreat. We found that the negative correlation between cloud fraction and sea-ice concentration is not as strong as that for the surface downwelling longwave flux. It indicates the increase in cloudiness may result in positive anomalies in surface downwelling longwave flux which is highly correlated with the sea-ice retreat in autumn.

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Influence of the Gulf Stream on the Barents Sea ice retreat and Eurasian coldness during early winter

Environmental Research Letters ◽

10.1088/1748-9326/9/8/084009 ◽

2014 ◽

Vol 9 (8) ◽

pp. 084009 ◽

Cited By ~ 97

Author(s):

Kazutoshi Sato ◽

Jun Inoue ◽

Masahiro Watanabe

Keyword(s):

Sea Ice ◽

Gulf Stream ◽

Barents Sea ◽

Early Winter ◽

The Barents Sea ◽

Ice Retreat ◽

Sea Ice Retreat

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Model-data comparison and data assimilation of mid-Holocene Arctic sea-ice concentration

Climate of the Past Discussions ◽

10.5194/cpd-9-6515-2013 ◽

2013 ◽

Vol 9 (6) ◽

pp. 6515-6549 ◽

Cited By ~ 1

Author(s):

F. Klein ◽

H. Goosse ◽

A. Mairesse ◽

A. de Vernal

Keyword(s):

Data Assimilation ◽

Sea Ice ◽

Atmospheric Circulation ◽

Barents Sea ◽

Arctic Sea Ice ◽

The Arctic ◽

Model Data ◽

Sea Ice Concentration ◽

Arctic Sea ◽

Ice Concentration

Abstract. The consistency between a new quantitative reconstruction of Arctic sea-ice concentration based on dinocyst assemblages and the results of climate models has been investigated for the mid-Holocene. The comparison shows that the simulated sea-ice changes are weaker and spatially more homogeneous than the recorded ones. Furthermore, although the model-data agreement is relatively good in some regions such as the Labrador Sea, the skill of the models at local scale is low. The response of the models follows mainly the increase in summer insolation at large scale. This is modulated by changes in atmospheric circulation leading to differences between regions in the models that are albeit smaller than in the reconstruction. Performing simulations with data assimilation using the model LOVECLIM amplifies those regional differences, mainly through a reduction of the southward winds in the Barents Sea and an increase in the westerly winds in the Canadian Basin of the Arctic. This leads to an increase in the ice concentration in the Barents and Chukchi Seas and a better agreement with the reconstructions. This underlines the potential role of atmospheric circulation to explain the reconstructed changes during the Holocene.

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Climatic trends of sea surface temperature and sea ice concentration in the Barents Sea

10.5194/egusphere-egu21-12813 ◽

2021 ◽

Author(s):

Bayoumy Mohamed ◽

Frank Nilsen ◽

Ragnheid Skogseth

Keyword(s):

Sea Ice ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Seasonal Cycle ◽

Barents Sea ◽

Warming Trend ◽

Sea Surface ◽

Sea Ice Concentration ◽

The Barents Sea ◽

Ice Concentration

Sea ice loss in the Arctic region is an important indicator for climate change. Especially in the Barents Sea, which is expected to be free of ice by the mid of this century (Onarheim et al., 2018). Here, we analyze 38 years (1982-2019) of daily gridded sea surface temperature (SST) and sea ice concentration (SIC) from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) project. These data sets have been used to investigate the seasonal cycle and linear trends of SST and SIC, and their spatial distribution in the Barents Sea. From the SST seasonal cycle analysis, we have found that most of the years that have temperatures above the climatic mean (1982-2019) were recorded after 2000. This confirms the warm transition that has taken place in the Barents Sea over the last two decades. The year 2016 was the warmest year in both winter and summer during the study period. &#160;&#160;Results from the linear trend analysis reveal an overall statistically significant warming trend for the whole Barents Sea of about 0.33&#177;0.03 &#176;C/decade, associated with a sea ice reduction rate of about -4.9&#177;0.6 %/decade. However, the SST trend show a high spatial variability over the Barents Sea. The highest SST trend was found over the eastern part of the Barents Sea and south of Svalbard (Storfjordrenna Trough), while the Northern Barents Sea shows less distinct and non-significant trends. The largest negative trend of sea ice was observed between Novaya Zemlya and Franz Josef Land. Over the last two decades (2000-2019), the data show an amplified warming trend in the Barents Sea where the SST warming trend has increased dramatically (0.46&#177;0.09 &#176;C/decade) and the SIC is here decreasing with rate of about -6.4&#177;1.5 %/decade.&#160; Considering the current development of SST, if this trend persists, the Barents Sea annual mean SST will rise by around 1.4 &#176;C by the end of 2050, which will have a drastic impact on the loss of sea ice in the Barents Sea.&#160; &#160;&#160;Keywords: Sea surface temperature; Sea ice concentration; Trend analysis; Barents Sea

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Quantifying the Influence of Atlantic Heat on Barents Sea Ice Variability and Retreat*

Journal of Climate ◽

10.1175/jcli-d-11-00466.1 ◽

2012 ◽

Vol 25 (13) ◽

pp. 4736-4743 ◽

Cited By ~ 228

Author(s):

M. Årthun ◽

T. Eldevik ◽

L. H. Smedsrud ◽

Ø. Skagseth ◽

R. B. Ingvaldsen

Keyword(s):

Sea Ice ◽

Heat Transport ◽

Barents Sea ◽

Heat Budget ◽

Heat Content ◽

Ocean Model ◽

Sea Ice Extent ◽

The Barents Sea ◽

Ice Retreat ◽

Sea Ice Retreat

Abstract The recent Arctic winter sea ice retreat is most pronounced in the Barents Sea. Using available observations of the Atlantic inflow to the Barents Sea and results from a regional ice–ocean model the authors assess and quantify the role of inflowing heat anomalies on sea ice variability. The interannual variability and longer-term decrease in sea ice area reflect the variability of the Atlantic inflow, both in observations and model simulations. During the last decade (1998–2008) the reduction in annual (July–June) sea ice area was 218 × 103 km2, or close to 50%. This reduction has occurred concurrent with an increase in observed Atlantic heat transport due to both strengthening and warming of the inflow. Modeled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport (r = −0.63) with a 70 × 103 km2 decrease per 10 TW input of heat. Based on the simulated ocean heat budget it is found that the heat transport into the western Barents Sea sets the boundary of the ice-free Atlantic domain and, hence, the sea ice extent. The regional heat content and heat loss to the atmosphere scale with the area of open ocean as a consequence. Recent sea ice loss is thus largely caused by an increasing “Atlantification” of the Barents Sea.

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