Arctic Sea Ice Melt Research Articles

Winter Sentinel‐1 Backscatter as a Predictor of Spring Arctic Sea Ice Melt Pond Fraction

AbstractSpring melt pond fraction (fp) has been shown to influence September sea ice extent and, with a growing need to improve melt pond physics in climate and forecast models, observations at large spatial scales are needed. We present a novel technique for estimating fp on sea ice at high spatial resolution from the Sentinel‐1 satellite during the winter period leading up to spring melt. A strong correlation (r = −0.85) is found between winter radar backscatter and fp from first‐year and multiyear sea ice data collected in the Canadian Arctic Archipelago (CAA) in 2015. Observations made in the CAA in 2016 are used to validate a fp retrieval algorithm, and a fp prediction for the CAA in 2017 is made. The method is effective using the horizontal transmit and receive polarization channel only and shows promise for providing seasonal, pan‐Arctic, fp maps for improved understanding of melt pond distributions and forecast model skill.

Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers

Abstract We determined, and compared, the abiotic stress state of algae and their attached bacterial communities following their release into the water column during the Arctic sea ice melt season using specific lipid markers that are characteristic of type II photo-oxidation processes, together with those associated with cis-trans isomerase and 10 S -DOX-like lipoxygenase activity, which are indicative of salinity stress. More specifically, parent lipids and some of their oxidation products were quantified in sinking particles (from sediment traps) collected from the Beaufort Sea, Resolute Passage and the Davis Strait (Canadian Arctic) in 2009, 2012 and 2015, respectively. Our data show that salinity- and light-induced bacterial stress processes are temporally decoupled, with the former occurring at the beginning of ice melting and the latter observed during the final stages of ice melt and in subsequent open waters. The salinity-induced bacterial stress seen during the early stages of ice melting contrasts the healthy state of sea ice algae under the same hypersaline conditions. As sea ice melt progresses, brine channels become hyposaline, thus reducing the bacterial salinity stress, while ice algae become susceptible to photodegradation by singlet oxygen ( 1 O 2 ), despite relatively low temperatures and irradiance. However, the presence of high amounts of extracellular polymeric substances (EPS) encapsulating the algae likely prevents the diffusion of 1 O 2 to the attached bacteria. Photo-oxidative stress is enhanced further in open waters due to the low amounts of EPS. The lower amounts of active bacteria in the Arctic compared to temperate or tropical regions is thus attributed to the combined action of efficient salinity stress in spring and photo-oxidative stress in summer. Outcomes from this study also imply that surface sediments from the Canadian Arctic contain relatively high quantities of sea ice-derived organic matter that has undergone a strong degree of salinity-induced stress.

Arctic sea ice melt leads to atmospheric new particle formation

Atmospheric new particle formation (NPF) and growth significantly influences climate by supplying new seeds for cloud condensation and brightness. Currently, there is a lack of understanding of whether and how marine biota emissions affect aerosol-cloud-climate interactions in the Arctic. Here, the aerosol population was categorised via cluster analysis of aerosol size distributions taken at Mt Zeppelin (Svalbard) during a 11 year record. The daily temporal occurrence of NPF events likely caused by nucleation in the polar marine boundary layer was quantified annually as 18%, with a peak of 51% during summer months. Air mass trajectory analysis and atmospheric nitrogen and sulphur tracers link these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. The occurrence of such events across a full decade was anti-correlated with sea ice extent. New particles originating from open water and open pack ice increased the cloud condensation nuclei concentration background by at least ca. 20%, supporting a marine biosphere-climate link through sea ice melt and low altitude clouds that may have contributed to accelerate Arctic warming. Our results prompt a better representation of biogenic aerosol sources in Arctic climate models.

Multicentennial record of Labrador Sea primary productivity and sea-ice variability archived in coralline algal barium

Accelerated warming and melting of Arctic sea-ice has been associated with significant increases in phytoplankton productivity in recent years. Here, utilizing a multiproxy approach, we reconstruct an annually resolved record of Labrador Sea productivity related to sea-ice variability in Labrador, Canada that extends well into the Little Ice Age (LIA; 1646 AD). Barium-to-calcium ratios (Ba/Ca) and carbon isotopes (δ13C) measured in long-lived coralline algae demonstrate significant correlations to both observational and proxy records of sea-ice variability, and show persistent patterns of co-variability broadly consistent with the timing and phasing of the Atlantic Multidecadal Oscillation (AMO). Results indicate reduced productivity in the Subarctic Northwest Atlantic associated with AMO cool phases during the LIA, followed by a step-wise increase from 1910 to present levels—unprecedented in the last 363 years. Increasing phytoplankton productivity is expected to fundamentally alter marine ecosystems as warming and freshening is projected to intensify over the coming century.

Towards a balanced view of Arctic shipping: estimating economic impacts of emissions from increased traffic on the Northern Sea Route

The extensive melting of Arctic sea ice driven by climate change provides opportunities for commercial shipping due to shorter travel distances of up to 40% between Asia and Europe. It has been estimated that around 5% of the world’s trade could be shipped through the Northern Sea Route (NSR) in the Arctic alone under year-round and unhampered navigability, generating additional income for many European and East Asian countries. Our analysis shows that for Arctic sea ice conditions under the RCP8.5 emissions scenario and business restrictions facing shipping companies, NSR traffic will increase steadily from the mid-2030s onwards, although it will take over a century to reach the full capacity expected for ice-free conditions. However, in order to achieve a balanced view of Arctic shipping, it is important to include its detrimental environmental impacts, most notably emissions of short-lived pollutants such as black carbon, as well as CO2 and non-CO2 emissions associated with the additional economic growth enabled by NSR. The total climate feedback of NSR could contribute 0.05% (0.04%) to global mean temperature rise by 2100 under RCP8.5 (RCP4.5), adding $2.15 trillion ($0.44 trillion) to the NPV of total impacts of climate change over the period until 2200 for the SSP2 socio-economic scenario. The climatic losses offset 33% (24.7%) of the total economic gains from NSR under RCP8.5 (RCP4.5), with the biggest losses set to occur in Africa and India. These findings call for policy instruments aimed at reducing emissions from Arctic shipping and providing compensation to the affected regions.

Radiocarbon in dissolved organic and inorganic carbon of the Arctic Ocean

AbstractDissolved organic carbon (DOC) in the ocean is thousands of 14C years old, yet a portion of the DOC cycles on much shorter time scales (days to decades). We present 14C measurements of DOC in the Arctic Ocean and estimate that ≥8% of the DOC in the deep Eurasian Basin contains bomb 14C. While this is a limited data set, there appears to be selective loss of modern DOC in the surface and halocline waters of the open Beaufort Sea versus the Beaufort slope. At one of the Beaufort Sea stations, there is a linear relationship between DOC Δ14C values and previously measured total hydrolysable amino acid concentrations as reported by Shen et al. (2012), indicating that deep DOC contains small amounts of bioavailable DOC. The 14C data show that not all of the deep DOC is recalcitrant.

Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP) F13 Special Sensor Microwave/Imagers (SSMI) and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS) sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/ or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA).

Predictability of Arctic Annual Minimum Sea Ice Patterns

Abstract Prediction of the arctic annual sea ice minimum extent and melting patterns draws interest from numerous industries and government agencies but has been an ongoing challenge for forecasters and climate scientists using statistical and dynamical models. Using the dominant independent modes of interannual sea ice concentration (SIC) variability during September–October, a new approach combining statistical analysis with physically derived links to natural climate variability sources is used to predict each mode and the total anomaly pattern. Sea ice patterns associated with each mode are predominantly shaped by the wind-driven advective convergence, forced by circulation anomalies associated with local and remote forms of naturally occurring climate variability. The impacts of the Arctic Oscillation, beginning from the preceding winter, control the leading mode of SIC variability during the annual minimum. In the three final months of the melting period, the broad impacts of the Indian and East Asian summer monsoons produce unique SIC impacts along the arctic periphery, displayed as the second and third modes, respectively. El Niño–Southern Oscillation (ENSO) largely shapes the fourth SIC mode patterns through influencing variability early in the melting period. Using physically meaningful and statistically significant predictors, physical–empirical (P–E) models are developed for each SIC mode. Some predictors directly account for the circulation patterns driving anomalous sea ice, while the monsoon-related predictors convey early season sources of monsoonal variability, which subsequently influences the Arctic. The combined SIC predictions of the P–E models exhibit great skill in matching the observed magnitude and temporal variability along the arctic margins during the annual minimum.

Unraveling the Teleconnection Mechanisms that Induce Wintertime Temperature Anomalies over the Northern Hemisphere Continents in Response to the MJO

Abstract Significant extratropical surface air temperature variations arise as a result of teleconnections induced by the Madden–Julian oscillation (MJO). The authors elucidate the detailed physical processes responsible for the development of temperature anomalies over Northern Hemisphere continents in response to MJO-induced heating using an intraseasonal perturbation thermodynamic equation and a wave activity tracing technique. A quantitative assessment demonstrates that surface air temperature variations are due to dynamical processes associated with a meridionally propagating Rossby wave train. Over East Asia, a local Hadley circulation causes adiabatic subsidence following MJO phase 3 to be a main driver for the warming. Meanwhile, for North America and eastern Europe, horizontal temperature advection by northerlies or southerlies is the key process for warming or cooling. A ray-tracing analysis illustrates that Rossby waves with zonal wavenumbers 2 and 3 influence the surface warming over North America and a faster wavenumber 4 affects surface temperature over eastern Europe. Although recent studies demonstrate the impacts of the Arctic Oscillation, Arctic sea ice melting, and Eurasian snow cover variations on extremely cold wintertime episodes over the NH extratropics, the weather and climate there are still considerably modulated through teleconnections induced by the tropical heat forcing. In addition, the authors show that the MJO is a real source of predictability for strong warm/cold events over these continents, suggesting a higher possibility of making a skillful forecast of temperature extremes with over 1 month of lead time.

Change in the air

Arctic Sea Ice![Figure][1] Sea ice near Kulusuk, Greenland PHOTO: ©INCAMERASTOCK/ALAMY STOCK PHOTO How does atmospheric circulation affect the initiation of seasonal melting of Arctic sea ice? Mortin et al. examined 35 years of satellite and meteorological data to tease out the general controls and explain the large annual variability in timing. They found that melt onset is triggered by high water vapor, clouds, and air temperatures, which act to increase the amount of long-wave radiation down-welling to the ice surface. Early melts occur when these conditions persist for weeks beforehand because of changes in springtime atmospheric moisture transport. Geophys. Res. Lett. 10.1002/2016GL069330 (2016). [1]: pending:yes

Shifting El Niño inhibits summer Arctic warming and Arctic sea-ice melting over the Canada Basin.

Arctic climate changes include not only changes in trends and mean states but also strong interannual variations in various fields. Although it is known that tropical-extratropical teleconnection is sensitive to changes in flavours of El Niño, whether Arctic climate variability is linked to El Niño, in particular on interannual timescale, remains unclear. Here we demonstrate for the first time a long-range linkage between central Pacific (CP) El Niño and summer Arctic climate. Observations show that the CP warming related to CP El Niño events deepens the tropospheric Arctic polar vortex and strengthens the circumpolar westerly wind, thereby contributing to inhibiting summer Arctic warming and sea-ice melting. Atmospheric model experiments can generally capture the observed responses of Arctic circulation and robust surface cooling to CP El Niño forcing. We suggest that identification of the equator-Arctic teleconnection, via the ‘atmospheric bridge', can potentially contribute to improving the skill of predicting Arctic climate.

Impacts of Polar Changes on the UV-induced Mineralization of Terrigenous Dissolved Organic Matter.

Local climates in the Northern and Southern Hemisphere are influenced by Arctic Amplification and by interactions of the Antarctic ozone hole with climate change, respectively. Polar changes may affect hydroclimatic conditions in temperate regions, for example, by increasing the length and intensity of precipitation events at Northern Hemisphere midlatitudes. Additionally, global warming has led to the thawing of ancient permafrost soils, particularly in Arctic regions, due to Arctic Amplification. Both heavy precipitation events and thawing of permafrost are increasing the net transfer of terrestrially derived dissolved organic matter (DOM) from land to surface waters. In aquatic ecosystems, UV-induced oxidation of terrigenous DOM (tDOM) produces atmospheric CO2 and this process is one of several mechanisms by which natural organic matter in aquatic and soil environments may play an important role in climate feedbacks. The Arctic is particularly affected by these processes: for example, melting of Arctic sea ice allows solar UV radiation to penetrate into the ice-free Arctic Ocean and to cause photochemical reactions that result in bleaching and mineralization of tDOM. Open questions, in addition to those shown in the Graphical Abstract, remain regarding the resulting contributions of tDOM photomineralization to CO2 production and global warming.

Predicting Summer Arctic Sea Ice Concentration Intraseasonal Variability Using a Vector Autoregressive Model*

Abstract Recent Arctic sea ice changes have important societal and economic impacts and may lead to adverse effects on the Arctic ecosystem, weather, and climate. Understanding the predictability of Arctic sea ice melting is thus an important task. A vector autoregressive (VAR) model is evaluated for predicting the summertime (May–September) daily Arctic sea ice concentration on the intraseasonal time scale, using only the daily sea ice data and without direct information of the atmosphere and ocean. The intraseasonal forecast skill of Arctic sea ice is assessed using the 1979–2012 satellite data. The cross-validated forecast skill of the VAR model is found to be superior to both the anomaly persistence and damped anomaly persistence at lead times of ~20–60 days, especially over northern Eurasian marginal seas and the Beaufort Sea. The daily forecast of ice concentration also leads to predictions of ice-free dates and September mean sea ice extent. In addition to capturing the general seasonal melt of sea ice, the model is also able to capture the interannual variability of the melting, from partial melt of the marginal sea ice in the beginning of the period to almost a complete melt in the later years. While the detailed mechanism leading to the high predictability of intraseasonal sea ice concentration needs to be further examined, the study reveals for the first time that Arctic sea ice can be predicted statistically with reasonable skill at the intraseasonal time scales given the small signal-to-noise ratio of daily data.

Influence of melt-pond depth and ice thickness on Arctic sea-ice albedo and light transmittance

Solar radiation drives the melting of Arctic sea ice in summer, but its parameterization in thermodynamic modeling is difficult due to the large variability of the optical properties of sea ice in space and time. Here, a two-stream radiative transfer model was developed for the propagation of solar radiation in ponded sea ice to investigate the dependence of apparent optical properties (AOPs), particularly albedo and transmittance, on sky conditions, pond depth, ice thickness, and the inherent optical properties (IOPs) of ice and water. The results of numerical experiments revealed that decrease in melt-pond albedo during melting results not only from increase in pond depth but also from decrease in underlying ice thickness, and the latter is more important for thin ice with thickness less than 1.5m. Hence, a parameterized pond albedo as a function of both pond depth and ice thickness is more suitable for thinning Arctic sea ice than the previously used exponential function of pond depth, which is valid for thicker ice. The increase in broadband transmittance during melting can be explained by the decrease in underlying ice thickness, because its dependence on ice thickness is nearly three times stronger than on pond depth. The spectral dependence of the pond albedo on depth is significant only in the 600–900-nm band, while it depends clearly on ice thickness in the 350–600-nm band. The uncertainty resulting from the absorption coefficient of ice is limited, while the effect of scattering in ice is more important, as determined by a sensitivity study on the influence of the IOPs on the AOPs of sea ice. The two-stream model provides a time-efficient parameterization of the AOPs for ponded sea ice, accounting for both absorption and scattering, and has potential for implementation into sea-ice thermodynamic models to explain the role of melt ponds in the summer decay of Arctic sea ice.

Atmospheric moisture transport: the bridge between ocean evaporation and Arctic ice melting

Abstract. Changes in the atmospheric moisture transport have been proposed as a vehicle for interpreting some of the most significant changes in the Arctic region. The increasing moisture over the Arctic during the last decades is not strongly associated with the evaporation that takes place within the Arctic area itself, despite the fact that the sea ice cover is decreasing. Such an increment is consistent and is more dependent on the transport of moisture from the extratropical regions to the Arctic that has increased in recent decades and is expected to increase within a warming climate. This increase could be due either to changes in circulation patterns which have altered the moisture sources, or to changes in the intensity of the moisture sources because of enhanced evaporation, or a combination of these two mechanisms. In this short communication we focus on the more objective assessment of the strong link between ocean evaporation trends and Arctic Sea ice melting. We will critically analyse several recent results suggesting links between moisture transport and the extent of sea ice in the Arctic, this being one of the most distinct indicators of continuous climate change both in the Arctic and on a global scale. To do this we will use a sophisticated Lagrangian approach to develop a more robust framework on some of these previous disconnecting results, using new information and insights. Results reached in this study stress the connection between two climate change indicators, namely an increase in evaporation over source regions (mainly the Mediterranean Sea, the North Atlantic Ocean and the North Pacific Ocean in the paths of the global western boundary currents and their extensions) and Arctic ice melting precursors.

Causes for different spatial distributions of minimum Arctic sea-ice extent in 2007 and 2012

Satellite records show the minimum Arctic sea ice extents (SIEs) were observed in the Septembers of 2007 and 2012, but the spatial distributions of sea ice concentration reduction in these two years were quite different. Atmospheric circulation pattern and the upper-ocean state in summer were investigated to explain the difference. By employing the ice-temperature and ice-specific humidity (SH) positive feedbacks in the Arctic Ocean, this paper shows that in 2007 and 2012 the higher surface air temperature (SAT) and sea level pressure (SLP) accompanied by more surface SH and higher sea surface temperature (SST), as a consequence, the strengthened poleward wind was favorable for melting summer Arctic sea ice in different regions in these two years. SAT was the dominant factor influencing the distribution of Arctic sea ice melting. The correlation coefficient is–0.84 between SAT anomalies in summer and the Arctic SIE anomalies in autumn. The increase SAT in different regions in the summers of 2007 and 2012 corresponded to a quicker melting of sea ice in the Arctic. The SLP and related wind were promoting factors connected with SAT. Strengthening poleward winds brought warm moist air to the Arctic and accelerated the melting of sea ice in different regions in the summers of 2007 and 2012. Associated with the rising air temperature, the higher surface SH and SST also played a positive role in reducing summer Arctic sea ice in different regions in these two years, which form two positive feedbacks mechanism.

Changes in weather and climate extremes over Korea and possible causes: A review

Weather and climate extremes exert devastating influence on human society and ecosystem around the world. Recent observations show increase in frequency and intensity of climate extremes around the world including East Asia. In order to assess current status of the observed changes in weather and climate extremes and discuss possible mechanisms, this study provides an overview of recent analyses on such extremes over Korea and East Asia. It is found that the temperature extremes over the Korean Peninsula exhibit long-term warming trends with more frequent hot events and less frequent cold events, along with sizeable interannual and decadal variabilities. The comprehensive review on the previous literature further suggests that the weather and climate extremes over East Asia can be affected by several climate factors of external and internal origins. It has been assessed that greenhouse warming leads to increase in warm extremes and decrease in cold extremes over East Asia, but recent Arctic sea-ice melting and associated warming tends to bring cold snaps to East Asia during winter. Internal climate variability such as tropical intraseasonal oscillation and El Nino-Southern Oscillation can also exert considerable impacts on weather and climate extremes over Korea and East Asia. It is, however, noted that our current understanding is far behind to estimate the effect of these climate factors on local weather and climate extremes in a quantitative sense.

Observed anomalous atmospheric patterns in summers of unusual Arctic sea ice melt

AbstractThe Arctic sea ice retreat has accelerated over the last decade. The negative trend is largest in summer, but substantial interannual variability still remains. Here we explore observed atmospheric conditions and feedback mechanisms during summer months of anomalous sea ice melt in the Arctic. Compositing months of anomalous low and high sea ice melt over 1979–2013, we find distinct patterns in atmospheric circulation, precipitation, radiation, and temperature. Compared to summer months of anomalous low sea ice melt, high melt months are characterized by anomalous high sea level pressure in the Arctic (up to 7 hPa), with a corresponding tendency of storms to track on a more zonal path. As a result, the Arctic receives less precipitation overall and 39% less snowfall. This lowers the albedo of the region and reduces the negative feedback the snowfall provides for the sea ice. With an anticyclonic tendency, 12 W/m2 more incoming shortwave radiation reaches the surface in the start of the season. The melting sea ice in turn promotes cloud development in the marginal ice zones and enhances downwelling longwave radiation at the surface toward the end of the season. A positive cloud feedback emerges. In midlatitudes, the more zonally tracking cyclones give stormier, cloudier, wetter, and cooler summers in most of northern Europe and around the Sea of Okhotsk. Farther south, the region from the Mediterranean Sea to East Asia experiences significant surface warming (up to 2.4°C), possibly linked to changes in the jet stream.

北极争端的症结及中国的北极战略定位 / The Sticking Point of the Arctic Dispute and China's Strategic Positioning

李诗隽 【摘要】 全球气候变暖导致北极冰川融化，这使得北极的价值突显。近年来，沿岸各国乃至圈外国围绕北极海洋主权、海域边界、资源开采、航道控制等海洋权益的地缘政治竞争愈演愈烈，而北极争端的症结则集中体现在能源、航道和地缘政治这三个问题上。面对美国、俄罗斯和加拿大各有侧重的北极战略，中国应以能源安全为战略基点，积极开展与北欧国家的多边合作，以经济合作为主，扩大北极非军事区域范围，从而能够在错综复杂地北极争端中最大限度地谋求国家利益。 Global climate warming results in Arctic sea ice melting which increases the value of the Arctic. In recent years, the competition among Arctic coastal nations and nations outside the Arctic has become increasingly fierce for sovereignty over the Arctic Ocean, sea borders, resource extraction, channel control, and other marine interests. The crux of the Arctic dispute focuses on energy, control of the waterways, and geopolitics. To face up to the United States, Russia and Canada’s Arctic strategies, China should focus on energy security strategy. China should actively carry out multilateral cooperation with the Nordic countries, mainly on economic cooperation, and expand the scope of the demilitarized zone, thus becoming able to maximize the interests of the Chinese state.

Arctic sea ice melt may be causing extreme weather

Arctic sea ice melt may be causing extreme weather