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Detailed micropaleontological analysis was performed on the sediment core AMK-6142 collected in the deep southwestern part of the Lofoten Basin in the Norwegian Sea. Summer sea-surface temperature for the 7 cal. ka BP was reconstructed from dinocyst assemblages using the modern analogue technique (MAT). Sea-surface reconstruction and dinocysts species composition indicate repeated changes in environmental conditions in the surface water layer during the Middle and Late Holocene. Episodes of cooling and probable displacement of the Arctic Front to the southwestern part of the Lofoten Basin were recorded for 5–7, 1.6–2.1, and 0.1–1.0 cal. ka BP.

Extratropical cyclone activity over the central Arctic Ocean reaches its peak in summer. Previous research has argued for the existence of two external source regions for cyclones contributing to this summer maximum: the Eurasian continent interior and a narrow band of strong horizontal temperature gradients along the Arctic coastline known as the Arctic frontal zone (AFZ). This study incorporates data from an atmospheric reanalysis and an advanced cyclone detection and tracking algorithm to critically evaluate the relationship between the summer AFZ and cyclone activity in the central Arctic Ocean. Analysis of both individual cyclone tracks and seasonal fields of cyclone characteristics shows that the Arctic coast (and therefore the AFZ) is not a region of cyclogenesis. Rather, the AFZ acts as an intensification area for systems forming over Eurasia. As these systems migrate toward the Arctic Ocean, they experience greater deepening in situations when the AFZ is strong at midtropospheric levels. On a broader scale, intensity of the summer AFZ at midtropospheric levels has a positive correlation with cyclone intensity in the Arctic Ocean during summer, even when controlling for variability in the northern annular mode. Taken as a whole, these findings suggest that the summer AFZ can intensify cyclones that cross the coast into the Arctic Ocean, but focused modeling studies are needed to disentangle the relative importance of the AFZ, large-scale circulation patterns, and topographic controls.

Arctic cyclones, as significant weather systems at high latitudes, are often accompanied by strong winds or heavy precipitation, leading to prolonged and more destructive disasters. In this study, we identified summer (JJAS) Arctic cyclones in the ERA5 reanalysis dataset from 1979 to 2022 using a machine-learning cyclone identification and tracking algorithm. We selected 40 sets of the strongest cyclones on the northern edge of Eurasia (NEE), one of the most identifiable Arctic Frontal Zones, over the past 44 years to assess the role of tropopause polar vortices (TPVs) in intense summer cyclones by using the Weather Research and Forecasting model (WRF). Our sensitivity experiments show that removing the horizontal temperature gradient of the lower stratosphere significantly reduces cyclone intensity, particularly for TPVs-matched cyclones, increasing by 7.4 hPa at their maximum intensity moment (2.8 hPa for TPVs-unmatched cyclones). TPVs-matched cyclones typically exhibit a lower tropopause and an “upper warm-lower cold” thermodynamic structure. High potential vorticity (PV) induced by the downward intrusion of TPVs due to the thermal structure closely links with the intensified development of these cyclones, leading to prolonged lifetimes. On the other hand, TPVs-unmatched cyclones display a distinct frontal structure in the lower troposphere but are not sensitive to changes in the upper-level horizontal temperature gradient. This may help to highlight the role of TPVs downward intrusion on TPVs-matched intense cyclones on NEE.

Understanding the climatological characteristics of marine cold air outbreaks (CAOs) is of critical importance to constrain the processes determining the heat flux forcing of the high-latitude oceans. In this study, a comprehensive multidecadal climatology of wintertime CAO air masses is presented for the Irminger Sea and Nordic seas. To investigate the origin, transport pathways, and thermodynamic evolution of CAO air masses, a novel methodology based on kinematic trajectories is introduced. The major conclusions are as follows: (i) The most intense CAOs occur as a result of Arctic outflows following Greenland’s eastern coast from the Fram Strait southward and west of Novaya Zemlya. Weak CAOs also originate in flow across the SST gradient associated with the Arctic Front separating the Greenland and Iceland Seas from the Norwegian Sea. A substantial fraction of Irminger CAO air masses originate in the Canadian Arctic and overflow southern Greenland. (ii) CAOs account for 60%–80% of the wintertime oceanic heat loss associated with few intense CAOs west of Svalbard and in the Greenland, Iceland, and Barents Seas and frequent weak CAOs in the Norwegian and Irminger Seas. (iii) The amount of sensible heat extracted by CAO air masses is set by their intensity and their pathway over the underlying SST distribution, whereas the amount of latent heat is additionally capped by the SST. (iv) Among all CAO air masses, those in the Greenland and Iceland Seas extract the most sensible heat from the ocean and undergo the most intense diabatic warming. Irminger SeaCAOair masses experience only moderate diabatic warming but pick up more moisture than the other CAO air masses.

The last interglacial interval was terminated by the inception of a long, progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth. However, the feedbacks, internal dynamics, and global teleconnections associated with declining northern summer insolation remain incompletely understood. Here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre (SPG) circulation of the North Atlantic Ocean. Detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from Ocean Drilling Program site 984 south of Iceland reveal repeated, progressive cold water-mass expansions into subpolar latitudes during the last peak interglacial interval, marine isotope substage 5e. These movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern Arctic front, and associated with rapid changes in the strength of the SPG. This persistent millennial-scale oceanographic oscillation accompanied a long-term cooling trend at a time of slowly declining northern summer insolation, providing an early link in the propagation of those insolation changes globally, and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent ∼100 ka.

Global warming results in increasingly widespread wildfires, mostly in Siberia, but also in North America and Europe, which are responsible for the uncontrollable emission of pollutants, also to the High Arctic region. This study examines 11 samples of rainfall collected in August in a coastal area of southern Bellsund (Svalbard, Norway). It covers detailed analysis of major ions (i.e., Cl−, NO3−, and SO42−) and elements (i.e., Cu, Fe, Mn, Pb, and Zn) to Hybrid Single-Particle Langrarian Integrated Trajectory( HYSPLIT) backward air mass trajectories. The research of wildfires, volcanic activities, and dust storms in the Northern Hemisphere has permitted the assessment of their relations to the fluctuations and origins of elements. We distinguished at least 2 days (27 and 28 August) with evident influence of volcanic activity in the Aleutian and Kuril–Kamchatka trenches. Volcanic activity was also observed in the case of the Siberian wildfires, as confirmed by air mass trajectories. Based on the presence of non-sea K (nsK), non-sea sulphates (nss), and Ca (the soil factor of burned areas), the continuous influence of wildfires on rainfall chemistry was also found. Moreover, dust storms in Eurasia were mainly responsible for the transport of Zn, Pb, and Cd to Svalbard. Global warming may lead to the increased deposition of mixed-origin pollutants in the summer season in the Arctic.

Alaskan Arctic waters have participated in hemispheric-wide Arctic warming over the last two decades at over twotimes the rate of global warming. During 2008-13, this relative warming occurred only north of the Bering Strait andthe atmospheric Arctic front that forms a north-south thermal barrier. This front separates the southeastern Bering Seatemperatures from Arctic air masses. Model projections show that future temperatures in the Chukchi and Beaufort seascontinue to warm at a rate greater than the global rate, reaching a change of ＋4℃ by 2040 relative to the 1981-2010mean. Offshore at 74~N, climate models project the open water duration season to increase from a current average of threemonths to five months by 2040. These rates are occasionally enhanced by midlatitude connections. Beginning in August2014, additional Arctic warming was initiated due to increased SST anomalies in the North Pacific and associated shiftsto southerly winds over Alaska, especially in winter 2015-16. While global warming and equatorial teleconnections areimplicated in North Pacific SSTs, the ending of the 2014-16 North Pacific warm event demonstrates the importance ofinternal, chaotic atmospheric natural variability on weather conditions in any given year. Impacts from global warming onAlaskan Arctic temperature increases and sea-ice and snow loss, with occasional North Pacific support, are projected tocontinue to propagate through the marine ecosystem in the foreseeable future. The ecological and societal consequences ofsuch changes show a radical departure from the current Arctic environment.

We quantify source contributions to springtime (April 2008) surface black carbon (BC) in the Arctic by interpreting surface observations of BC at five receptor sites (Denali, Barrow, Alert, Zeppelin, and Summit) using a global chemical transport model (GEOS-Chem) and its adjoint. Contributions to BC at Barrow, Alert, and Zeppelin are dominated by Asian anthropogenic sources (40–43 %) before 18 April and by Siberian open biomass burning emissions (29–41 %) afterward. In contrast, Summit, a mostly free tropospheric site, has predominantly an Asian anthropogenic source contribution (24–68 %, with an average of 45 %). We compute the adjoint sensitivity of BC concentrations at the five sites during a pollution episode (20–25 April) to global emissions from 1 March to 25 April. The associated contributions are the combined results of these sensitivities and BC emissions. Local and regional anthropogenic sources in Alaska are the largest anthropogenic sources of BC at Denali (63 % of total anthropogenic contributions), and natural gas flaring emissions in the western extreme north of Russia (WENR) are the largest anthropogenic sources of BC at Zeppelin (26 %) and Alert (13 %). We find that long-range transport of emissions from Beijing–Tianjin–Hebei (also known as Jing–Jin–Ji), the biggest urbanized region in northern China, contribute significantly (∼ 10 %) to surface BC across the Arctic. On average, it takes ∼ 12 days for Asian anthropogenic emissions and Siberian biomass burning emissions to reach the Arctic lower troposphere, supporting earlier studies. Natural gas flaring emissions from the WENR reach Zeppelin in about a week. We find that episodic transport events dominate BC at Denali (87 %), a site outside the Arctic front, which is a strong transport barrier. The relative contribution of these events to surface BC within the polar dome is much smaller (∼ 50 % at Barrow and Zeppelin and ∼ 10 % at Alert). The large contributions from Asian anthropogenic sources are predominately in the form of chronic pollution (∼ 40 % at Barrow, 65 % at Alert, and 57 % at Zeppelin) on about a 1-month timescale. As such, it is likely that previous studies using 5- or 10-day trajectory analyses strongly underestimated the contribution from Asia to surface BC in the Arctic.

On 24 February 2019, strong winds behind an Arctic cold front led to widespread blowing snow across the northern Great Plains including areas in eastern North/South Dakota and western Minnesota. Impacts of the event ranged from blizzard conditions in northwest Minnesota to sporadic, minor reductions in visibility across the region. This study documents the event using remotely sensed observations from platforms including geostationary and polar-orbiting satellites, an S-band radar, and time-lapse images from a camera located at the University of North Dakota in Grand Forks, North Dakota. Blowing snow is observed as plumes that resemble horizontal convective rolls (HCRs). Variations in near-infrared imagery are documented, and supporting observations suggest this is due to the occurrence or absence of clouds on top of the blowing snow layer. While lack of in situ observations preclude further investigation of physical differences between plumes, the utility of the Geostationary Operational Environmental Satellite-16 (GOES-16) satellite to operational forecasters is discussed. Improvements to spatial, radiometric, and temporal resolution courtesy of the Advanced Baseline Imager (ABI) on board GOES-16 allows for daytime detection of blowing snow events that previously, was only possible with instruments on board polar-orbiting satellites. This has improved Impact-Based Decision Support Services (IDSS) at National Weather Service offices that deal with the hazard of blowing snow.

The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud types (high cloud, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus, and deep convection) and three phases (ice, mixed, and water) in the Arctic. Possible reasons for the observed interannual variability are also discussed. The main conclusions are as follows: (1) More water clouds occur on the Atlantic side, and more ice clouds occur over continents. (2) The average spatial and seasonal distributions of cloud types show three patterns: high clouds and most cumuliform clouds are concentrated in low-latitude locations and peak in summer; altostratus and nimbostratus are concentrated over and around continents and are less abundant in summer; stratocumulus and stratus are concentrated near the inner Arctic and peak during spring and autumn. (3) Regional averaged interannual frequencies of ice clouds and altostratus clouds significantly decrease, while those of water clouds, altocumulus, and cumulus clouds increase significantly. (4) Significant features of the linear trends of cloud frequencies are mainly located over ocean areas. (5) The monthly water cloud frequency anomalies are positively correlated with air temperature in most of the troposphere, while those for ice clouds are negatively correlated. (6) The decrease in altostratus clouds is associated with the weakening of the Arctic front due to Arctic warming, while increased water vapor transport into the Arctic and higher atmospheric instability lead to more cumulus and altocumulus clouds.