Sea Ice Research Articles

North Atlantic and the Barents Sea variability contribute to the 2023 extreme fire season in Canada

In the late spring to summer season of 2023, Canada witnessed unprecedented wildfires, with an extensive burning area and smoke spreading as far as the East Coast of the United States and Europe. Here, using multisource data analysis and climate model simulations, we show that an abnormally warm North Atlantic, as well as an abnormally low Barents Sea ice concentration (SIC), are likely key climate drivers of this Canadian fire season, contributing to ~80% of the fire weather anomaly over Canada from June to August 2023. Specifically, the warm North Atlantic forms an anomalous regional zonal cell with ascending air over the Atlantic and descending air encircling Canada, creating hot and dry local conditions. Meanwhile, reduced Barents SIC leads to a high-pressure center and reinforces the dry northern winds in Canada through Rossby wave dynamics. These exacerbated dry and hot conditions create a favorable environment for the ignition and spread of fires, thus contributing to the prolonged and extreme fire season in Canada. These teleconnections can extend to decadal scales and have important implications for understanding and predicting decadal fire activity in Canada and the surrounding regions.

A Novel Cold‐Adapted Catechol 1,2‐Dioxygenase From Antarctic Sea‐Ice Bacterium Halomonas sp. ANT108: Characterization and Immobilization

ABSTRACTThe enzyme catechol 1,2‐dioxygenase (CAT) plays a critical role in the biosynthesis pathway of cis, cis‐muconic acid (CCMA), which serves as an indispensable raw material for various industrial applications. In this research, we cloned a novel cold‐adapted CAT (HaCAT) from the Antarctic sea ice bacterium Halomonas sp. ANT108. Homology modeling analysis revealed that HaCAT possessed the characteristic Fe3+ binding site and catalytic active site of typical CATs, and it exhibited unique structural adaptations to cold environments. The optimal temperature and pH for recombinant HaCAT (rHaCAT) were found to be 25°C and 6.5, respectively. At 0°C, the enzyme retained a maximum activity of 43.6%, and in the presence of 1.0 M NaCl, its activity reached 173.9%, demonstrating significant salt tolerance. Additionally, the Vmax and Km of rHaCAT were 6.68 μmol/min/mg and 128.90 μM at 25°C, respectively. Furthermore, rHaCAT was successfully immobilized in the metal‐organic framework ZIF‐8 and retained almost 50% of its activity after five reuse cycles, demonstrating excellent reusability. Overall, these results provided a new resource and theoretical foundation for the industrial biocatalytic production and modification of CAT.

Southerly winds and rapid sea ice reductions along the Sea of Okhotsk coast of Hokkaido

Southerly winds and rapid sea ice reductions along the Sea of Okhotsk coast of Hokkaido

The Summer North Atlantic Oscillation, Arctic sea ice, and Arctic jet Rossby wave forcing.

We use Coupled Model Intercomparison Project Phase 6 (CMIP6) coupled and Atmospheric Model Intercomparison Project (AMIP) climate models, dynamical analyses, and observations to investigate interactions between summer Arctic sea ice concentration (SIC) variations and the Summer North Atlantic Oscillation (SNAO). Observations suggest that SIC-SNAO relationships mainly come from the East Siberian to Arctic Canada (ESAC) region where a weak atmospheric jet stream exists in summer. Twelve CMIP6 models with the most realistic atmospheric climatologies over the North Atlantic and Europe agree well with reanalyses on relationships between SIC and Northern Hemisphere atmospheric circulation. CMIP6 model data indicate that ESAC SIC influences the SNAO with a lead time of several weeks. However, AMIP simulations do not reproduce the observed atmospheric circulation when observed sea ice is prescribed. Rossby wave analyses do though support observed ESAC SIC influences on the SNAO. We conclude that ESAC Arctic SIC modestly influences the SNAO, and such investigations require the use of coupled models.

Contrasting Precipitation Variations over the Himalayas–Southeastern Tibetan Plateau in Winter: Insights from the Perspectives of Anthropogenic Warming and Arctic Sea Ice Variations

Abstract Climate warming has caused widespread glacier retreat across the Tibetan Plateau (TP), with notable impacts observed in both the western Himalayas and southeastern TP. Remarkably, over the past two decades, the rate of glacier mass loss has remained stable or even declined in the western Himalayas, whereas a contrasting trend of acceleration has been evident in the southeastern TP. Among various factors considered, the contrasting winter precipitation pattern across the Himalayas–southeastern TP stands out as an important contributor to the observed differences in glacier mass balances. However, the underlying mechanisms behind this phenomenon remain unclear. Here, we provide evidence of a noticeable shift in the climate regime due to anthropogenic warming, altering atmospheric circulation patterns. This, in turn, has led to a significant change in the dominant winter precipitation pattern, favoring the observed contrasting glacier mass balances trend in winter. Additionally, the Barents–Kara Sea ice has emerged as a plausible driver of the interannual variability of the contrasting precipitation pattern, acting by exerting force on the atmosphere and stimulating the Rossby wave propagation. Consequently, it led to the opposite vertical motion and alterations in the moisture budget between the western Himalayas and southeastern TP. Thus, it is crucial to consider the unprecedented anthropogenic warming and Arctic Sea ice variations as potential drivers shaping both past and future glacier behaviors within this domain.

Spatio-temporal variations of the heat fluxes at the ice-ocean interface in the Bohai Sea

Thermodynamic process between the ice and the ocean plays a critical role in the evolution of sea-ice growth and melting in marginal seas. At the ice-ocean interface, the oceanic heat flux and the conductive heat flux transmitted through the ice layer jointly determine the latent heat flux driving the phase change (i.e., ice freezing/melting). In this study, the determination of two important thermal parameters in the ice module of the HAMSOM ice-ocean coupled model, namely the mixed layer thickness and the heat exchange coefficient at the ice-ocean interface, has been adjusted to improve the model performance. Spatio-temporal variations of heat fluxes at the ice-ocean interface in the Bohai Sea are investigated, based on the validated sea ice simulation in the 2011/2012 ice season. The relationships between the interfacial heat fluxes and oceanic and atmospheric conditioning factors are identified. We found that the surface conductive heat flux through ice shows short-term fluctuations corresponding to the atmospheric conditions, the magnitude of these fluctuations decreases with depth in the ice layer, likely due to reduced influence from atmospheric conditions at greater depths. Atmospheric conditions are the key controlling factors of the conductive heat flux through ice, while the oceanic heat flux is mainly controlled by the oceanic conditions (i.e., mixed layer temperature). Spatially, the value of the oceanic heat flux is larger in the marginal ice zone with relatively thin ice than in the inner ice zone with relatively thick ice. In the Bohai Sea, when ice is growing, heat within the ice layer is transferred upward from the ice base, and the heat is losing at the ice-ocean interface. This heat loss in the inner ice zone is obviously greater than that in the marginal ice zone. Whereas when ice is melting, the opposite is true.

Seasonal evolution modes of tropical sea surface temperature anomalies and their links to antarctic sea ice anomalies

Abstract Previous studies have explored the teleconnections between variability of Antarctic sea ice cover and tropical sea surface temperature (SST) across the Pacific, Atlantic, and Indian Ocean basins, typically focusing on each basin individually. However, there has been limited investigation into the impact of tropical SSTs—particularly from a seasonal evolution perspective—on Antarctic sea ice cover. In this study, we employ the self-organizing map method to identify and analyze the primary modes of seasonal SST evolution in the tropical oceans from 1854 to 2022. We also project changes in the frequency of these modes through the 21st century. Moreover, we examine the seasonal variability of Antarctic sea ice concentration in relation to these tropical SST modes over the past four decades. Our results reveal that tropical SST anomalies display both uniform and shifted seasonal evolution patterns. Notably, the frequency of switched modes—namely, transitions from La Niña to El Niño (node 8) and from El Niño to La Niña (node 3)—is expected to increase in future climate. Interestingly, nearly mirrored SST seasonal evolution patterns do not lead to entirely opposite atmospheric circulation anomalies in the southern mid-high latitudes, nor do they result in completely inverse Antarctic sea ice cover anomalies.

The annual cycle and sources of relevant aerosol precursor vapors in the central Arctic during the MOSAiC expedition

Abstract. In this study, we present and analyze the first continuous time series of relevant aerosol precursor vapors from the central Arctic (north of 80° N) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. These precursor vapors include sulfuric acid (SA), methanesulfonic acid (MSA), and iodic acid (IA). We use FLEXPART simulations, inverse modeling, sulfur dioxide (SO2) mixing ratios, and chlorophyll a (chl a) observations to interpret the seasonal variability in the vapor concentrations and identify dominant sources. Our results show that both natural and anthropogenic sources are relevant for the concentrations of SA in the Arctic, but anthropogenic sources associated with Arctic haze are the most prevalent. MSA concentrations are an order of magnitude higher during polar day than during polar night due to seasonal changes in biological activity. Peak MSA concentrations were observed in May, which corresponds with the timing of the annual peak in chl a concentrations north of 75° N. IA concentrations exhibit two distinct peaks during the year, namely a dominant peak in spring and a secondary peak in autumn, suggesting that seasonal IA concentrations depend on both solar radiation and sea ice conditions. In general, the seasonal cycles of SA, MSA, and IA in the central Arctic Ocean are related to sea ice conditions, and we expect that changes in the Arctic environment will affect the concentrations of these vapors in the future. The magnitude of these changes and the subsequent influence on aerosol processes remains uncertain, highlighting the need for continued observations of these precursor vapors in the Arctic.

Baffin Bay Ice Export and Production From Sentinel‐1, the RADARSAT Constellation Mission, and CryoSat‐2: 2016–2022

AbstractBaffin Bay is located between Greenland and several islands of the Canadian Arctic, providing a conduit for the downstream transport of ice and freshwater to the North Atlantic via Davis Strait. Using satellite observations from Sentinel‐1, the RADARSAT Constellation Mission, and CryoSat‐2, we estimated the sea ice export through Davis Strait and winter ice production in Baffin Bay from 2016 to 2022. The average annual ice export for this 6‐year period was 981 ± 193 × 103 km2 for area 816 ± 130 km3 for volume, and 653 ± 130 km3 for solid freshwater, all of which are considerably higher than previously reported estimates. The average winter ice area production upstream of Davis Strait was 758 × 103 km2 and the volume production was 589 km3 indicating that more than 80% of the ice exported out of Baffin Bay was produced locally. Compared to Fram Strait, sea ice fluxes through Davis Strait represent ∼59% of the volume and ∼111% of the area.

Evaluation of sea surface temperature from ocean reanalysis products over the North Indian Ocean

Ocean and sea ice reanalyses (ORAs or ocean syntheses) are reconstructions of the ocean and sea ice states using an ocean model integration constrained by atmospheric surface forcing and ocean observations via a data assimilation method. Ocean reanalyses are a valuable tool for monitoring and understanding long-term ocean variability at depth, mainly because this part of the ocean is still largely unobserved. Sea surface temperature (SST) is the key variable that drives the air–sea interaction process on different time scales. Despite improvements in model and reanalysis schemes, ocean reanalyses show errors when evaluated with independent observations. The independent evaluation studies of SST from ocean reanalysis over the Indian Ocean are limited. In this study, we evaluated the SST from 10 reanalysis products (ECCO, BRAN, SODA, NCEP-GODAS, GODAS-MOM4p1, ORAS5, CGLORS, GLORYS2V4, GLOSEA, and GREP) and five synthetic observation products (COBE, ERSST, OISST, OSTIA, and HadISST) and from the pure observation-based product AMSR2 for 2012–2017 with 12 in-situ buoy observations (OMNI) over the Arabian Sea and Bay of Bengal. Even though the reanalysis and observational products perform very well in the open ocean, the performance is poorer near the coast and islands. The reanalysis products perform comparatively better than most of the observational products. COBE and OISST perform better among the synthetic observational products in the northern Indian Ocean. GODAS-MOM4p1 and GREP performs best among the reanalysis products, often surpassing the observational products. ECCO shows poorer performance and higher bias in the Bay of Bengal. Comparing the BRAN daily and monthly SST, the monthly SST performance of reanalysis is better than the daily time scale.

Metagenomic inference of microbial community composition and function in the weathering crust aquifer of a temperate glacier

Bacterial, fungal, and algal communities that colonize aquatic systems on glacial ice surfaces mediate biogeochemical reactions that alter meltwater composition and affect meltwater production and storage. In this study, we sought to improve understanding of microbial communities inhabiting the shallow aquifer that forms seasonally within the ice surface of a glacier’s ablation zone (i.e., the weathering crust aquifer). Using a metagenomic approach, we compared gene contents of microbial assemblages in the weathering crust aquifer (WCA) of the Matanuska Glacier (Alaska, USA) to those recovered from supraglacial features and englacial ice. High abundances of Pseudomonadota, Cyanobacteriota, Actinomycetota, and Bacteroidota were observed across all samples, while taxa in class Gammaproteobacteria were found at significantly higher abundances in the weathering crust aquifer. The weathering crust aquifer samples also contained higher abundances of Dothideomycetes and Microbotryomyetes; fungal classes commonly observed in snow and other icy ecosystems. Phylogenetic analysis of 18S rRNA and rbcL gene sequences indicated high abundances of algae in the WCA that are closely related (> 98% and > 93% identity, respectively) to taxa of Ancylonema (Streptophyta) and Ochromonas (Ochrophyta) reported from glacial ice surfaces in Svalbard and Antarctic sea ice. Many functional gene categories (e.g., homeostasis, cellular regulation, and stress responses) were enriched in samples from the weathering crust aquifer compared to those from proximal englacial and supraglacial habitats, providing evidence for ecological specialization in the communities. The identification of phagotrophic phytoflagellate taxa and genes involved in mixotrophy implies that combined phototrophic and heterotrophic production may assist with persistence in the low light, low energy, and ephemeral conditions of the weathering crust environment. The compositional and functional differences we have documented indicate distinct microbial distributions and functional processes occur in the weathering crust aquifer environment, and we discuss how deciphering these nuances is essential for developing a more complete understanding of ecosystem biogeochemistry in supraglacial hydrological systems.

More or Less Ice? Shipping in the Russian Arctic and the Role of Climate Change

Melting sea ice has often been presented as a primary driver for development of Arctic shipping, but what role has it played for policies to develop the Northern Sea Route? It may look paradoxical that Russia has embarked on an ambitious icebreaker construction program, given climate change. In Russia, there have been contradictory assessments of further climate developments in the Arctic. Representatives of the nuclear icebreaker fleet have argued that a new cooling period will soon occur, whereas Russian climate science is dominated by unidirectional climate change. Nevertheless, there is agreement that more icebreakers are needed, since shipping activity is expected to increase, and an extended navigation season is an indisputable goal. Nuances in Russian climate science do not seem to play any role in policy planning for Arctic shipping. Shipping through the Arctic emits less greenhouse gases than navigation on conventional southerly routes, which may be used as an argument in favor of the Northern Sea Route. It is doubtful, though, that this will change priorities of international shipping companies, especially as long as international shipping is not subject to emissions standards. Many other considerations will have precedence. Obviously, Russia’s war in Ukraine and the ensuing international tension is affecting trade patterns and investments in the Russian Arctic. In this situation climate change plays less of a role in the development of shipping in the Russian Arctic. But even before the war climate change was less important than often assumed in the international literature.

The first firn core from Peter I Island – capturing climate variability across the Bellingshausen Sea

Abstract. Peter I Island is situated in the Bellingshausen Sea, a region that has experienced considerable climate change in recent decades. Warming sea surface temperatures and reduced sea ice cover have been accompanied by warming surface air temperature, increased snowfall, and accelerated mass loss over the adjacent ice sheet. Here we present data from the first firn core drilled on Peter I Island, spanning the period 2001–2017 CE. The stable water isotope data capture regional changes in surface air temperature and precipitation (snow accumulation) at the site, which are highly correlated with the surrounding Amundsen–Bellingshausen seas and the adjacent Antarctic Peninsula (r > 0.6, p < 0.05). The firn core data, together with the unique in situ data from an automatic weather station, confirm the high skill of the ERA5 reanalysis in capturing daily mean temperature and inter-annual precipitation variability, even over a small sub-Antarctic island. This study demonstrates the suitability of Peter I Island for future deep-ice-core drilling, with the potential to provide a valuable archive to explore ice–ocean–atmosphere interactions over decadal to centennial timescales for this dynamic region.

Key processes controlling the variability of the summer marine CO2 system in Fram Strait surface waters

The aim of this study was to decouple and quantify the influence of various biological and physical processes on the structure and variability of the marine carbonate system in the surface waters of the eastern part of the Fram Strait area. This productive region is characterized by its complex hydrographic and sea ice dynamics, providing an ideal set up to study their influence on the variability of the marine carbonate system. Different variables of the marine CO2 system: Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), partial pressure of CO2 (pCO2), and pH, were analysed together with temperature, salinity, sea ice extension, and chlorophyll a distribution during three consecutive summers (2019, 2020 and 2021), each of them having a unique oceanographic setting. The data revealed that TA and DIC are mostly controlled by the mixing of Atlantic water and sea ice meltwater. The combined effects of organic matter production/remineralization, calcium carbonate precipitation/dissolution, and air/sea CO2 gas exchange cause deviations from this salinity-related mixing. The scale of these deviations and the proportion between the effects observed for TA and DIC suggest interannual shifts in net primary production and dominant phytoplankton species in the area. These shifts are correlated with the sea ice extent and the spread of the Polar Surface Waters in the region. Net primary production is the main factor controlling the temporal and spatial variability of pH and pCO2 in the study area followed by the influence of temperature and, mixing of water masses expressed with salinity (seawater freshening). Surface waters of the Fram Strait area were generally undersaturated in CO2. The lowest pCO2 values, coinciding with an increase in oxygen saturation, were observed in areas of mixing of Arctic and Atlantic-derived water masses. However, as shown for 2021, a reduction of the sea ice extent may induce a westward shift of the chlorophyll maximum, resulting in pCO2 increase and pH decrease in the eastern part. This indicates that sea ice extent and associated spread of Polar Surface Waters may be important factors shaping primary production, and thus pCO2 and pH, in the Fram Strait area.

Stratigraphy and paleontology (plant and arthropod fossils) from the Late Neogene Niguanak site, Arctic Slope, Northern Alaska

ABSTRACT Motivated by the need for more paleodata for Pliocene paleoclimate data-model comparison, we revisited unpublished investigations of a fossiliferous site on the Niguanak River in Arctic North America. Analyses of the samples indicates forested conditions during an early phase of sedimentation in which environments were perhaps similar to those near tree line in the modern Anchorage area or farther south along the Pacific coast, whereas during a later phase of sedimentation, environments were characterized by shrub tundra vegetation and were possibly similar to the present-day conditions in the interior of southern Seward Peninsula. We describe the site stratigraphy and discuss the macrofossils and pollen recovered from the sediments, their paleoecological implications, and their significance for paleoclimate and sea ice. Mean annual temperatures were found to be 12.7°C warmer than current, with a pattern of much warmer winters, and less difference in summer warming as observed at other Pliocene Arctic sites. Finally, we discuss possible age assignments for the sediments, based on regional stratigraphy and geomorphology, and the probable sequence of evolution of arctic borderland climate and ecosystems.

Coastal lake sediments from Arctic Svalbard suggest colder summers are stormier.

The Arctic is rapidly losing its sea ice cover while the region warms faster than anywhere else on Earth. As larger areas become ice-free for longer, winds strengthen and interact more with open waters. Ensuing higher waves also increase coastal erosion and flooding, threatening communities and releasing permafrost carbon. However, the future trajectory of these changes remains poorly understood as instrumental observations and geological archives remain rare and short. Here, we address this critical knowledge gap by presenting a continuous Holocene-length reconstruction of Arctic eolian activity using coastal lake sediments from Svalbard. Exposed to both polar Easterlies and Westerly storm tracks, sheltered by a bedrock barrier, and subjected to little post-glacial uplift, our study site provides a stable baseline to assess Holocene changes in the dominant wind systems of the Barents Sea region. To do so with high precision, we rely on multiple independent lines of proxy evidence for wind-blown sediment input. Our reconstructions reveal quasi-cyclic summer wind maxima during regional cold periods, and challenge the view that a warmer and less icy future Arctic will be stormier.

The Vertical Structure of Turbulence Kinetic Energy Near the Arctic Sea‐Ice Surface

AbstractAtmospheric turbulence over the Arctic sea‐ice surface has been understudied due to the lack of observational data. In this study, we focus on the turbulence kinetic energy (TKE) over sea ice and distinguish its two different vertical structures, the “Surface” type and the “Elevated” type, using observations during the Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition (MOSAiC). The “Surface” type has the maximum TKE near the surface (at 2 m), while the “Elevated” type has the maximum TKE at a higher level (6 m). The TKE budget analysis indicates that the “Elevated” type is caused by the increased shear production of TKE at 6 m. In addition, spectral analysis reveals that the contribution to TKE by horizontal large eddies is enhanced in the “Elevated” type. Finally, how the vertical structure of TKE affects the parameterization of turbulent momentum flux is discussed.

Antarctic sea ice multidecadal variability triggered by Southern Annular Mode and deep convection

Antarctic sea ice exerts great influence on Earth’s climate by controlling the exchange of heat, momentum, freshwater, and gases between the atmosphere and ocean. Antarctic sea ice extent has undergone a multidecadal slight increase followed by a substantial decline since 2016. Here we utilize a 300-yr sea ice data assimilation reconstruction and two NOAA/GFDL and five CMIP6 model simulations to demonstrate a multidecadal variability of Antarctic sea ice extent. Stronger westerlies associated with the Southern Annular Mode (SAM) enhance the upwelling of warm and saline water from the subsurface ocean. The consequent salinity increase weakens the upper-ocean stratification, induces deep convection, and in turn brings more subsurface warm and saline water to the surface. This salinity-convection feedback triggered by the SAM provides favorable conditions for multidecadal sea ice decrease. Processes acting in reverse are found to cause sea ice increase, although it evolves slower than sea ice decrease.

Opposed east-west climate response of the Arctic Ocean during the present interglacial.

The role of the Arctic Ocean in the global climate system during the last climatic cycles remains conjectural, but radiocarbon-based chronologies and proxy data provide reliable information about the present interglacial. In the western Arctic, paleoceanographic data demonstrate a linkage between increasing Pacific water fluxes, resulting from the postglacial submergence of the Bering Strait, and the progressive warming, until climate conditions stabilized when sea level reached its present-day limit during the late Holocene. Meanwhile, the southeastern Arctic Ocean evolved from optimal conditions toward a perennial sea ice cover with cooling. We hypothesize that sea level, which determines the depth of Bering Strait and the submergence of the Arctic shelves, has led to enhanced production of seasonal sea ice and an increased freshwater export to the North Atlantic Ocean, since the onset of the present interglacial until preindustrial time.

Antarctic extreme seasons under 20th and 21st century climate change

In this study, available large ensemble datasets in the Coupled Model Intercomparison Phase 6 (CMIP6) archive were used to provide the first multi-variate overview of the evolution of extreme seasons over Antarctica and the Southern Ocean during the 20th and 21st centuries following medium-to-high radiative forcing scenarios. The results show significant differences between simulated changes in background mean climate and changes in low (10th percentile) and high (90th percentile) extreme seasons. Regional winter warming is most pronounced for cold extremes. In summer, there are more pronounced increases in high extremes in precipitation and westerly wind during the ozone hole formation period (late 20th century), affecting coastal regions and, in particular, the Antarctic Peninsula. At midlatitudes, there is a reduction in the range of summer season wind extremes. Suggested mechanisms for these differences are provided relating to sea ice retreat and westerly jet position.