Search

In situ meteorological data are essential to better understand ongoing environmental changes in the Arctic. Here, we present a dataset of quality-controlled meteorological observations by two automatic weather stations in northwest Greenland from July 2012 to the end of August 2020. The stations were installed in an accumulation area on the Greenland Ice Sheet (SIGMA-A site, 1490 m a.s.l.) and near the equilibrium line of the Qaanaaq Ice Cap (SIGMA-B site, 944 m a.s.l.). We describe the two-step sequence of quality-control procedures that we used to create increasingly reliable datasets by masking erroneous data records. We analyzed the resulting 2012-2020 time series of air temperature, positive degree-days, snow height, surface albedo, and histograms of longwave radiation (a proxy of cloud formation frequency). We found that snow height increased and albedo remained steady at the SIGMA-A site, whereas high air temperatures and clear-sky conditions prevailed while snow height and albedo decreased in the summers of 2015, 2019, and 2020 at the SIGMA-B site. Therefore, it appears that these weather conditions led to notable snow height degradation at the SIGMA-B site but not at the SIGMA-A site. We anticipate that this quality-control method and these datasets will aid in climate studies of northwest Greenland as well as contribute to the advancement of broader polar climate studies. [ABSTRACT FROM AUTHOR]

We provide the northernmost permafrost thermal analysis in Greenland through the ground temperature time series (2014–2021) and cryostratigraphy of two 20‐m deep boreholes (SN1 and SN2) at Villum Research Station, Station Nord (81°N). Three sedimentary units are identified in the stratigraphy: glacial, glaciomarine, and beach deposits. These sandy and gravelly deposits are interpreted to comprise a deglaciation and isostatic emergence sequence. Ice‐poor epigenetic permafrost grew downwards into the deposits following subaerial exposure. Relatively high salinity values (up to 70 ppt) are observed in the glaciomarine unit, resulting in freezing point depressions between 0 and −4°C. The Prinsesse Ingeborg Halvø study area has a polar tundra climate and is unique compared to other high Arctic areas because of a thick (>1 m), long‐lasting snow cover. This snow cover results in relatively high permafrost temperatures for the climate and latitude and the warmest known permafrost north of 80°N. Over the seven‐year study period, average 20 m permafrost temperature was −7.87°C at SN1 and −7.06°C at SN2. The warming rate at 20 m depth was 0.07°C/year at SN1 and 0.05°C/year at SN2, rates which are similar to those of other high Arctic sites. Active layer thickness, extrapolated from the temperature measurements, varied between 0.5 and 1.16 m. The interplay between snow dynamics and seasonal air temperature controls ground thermal regime in the study area. Air temperatures during autumn and midwinter, the fastest warming seasons, influence the ground thermal regime through the gradually developing, dense snowpack. Plain Language Summary: Permafrost, ground that is frozen for at least two consecutive years, is commonly found in high mountains and polar environments. Permafrost samples and long‐term permafrost temperature records are necessary to fully understand permafrost and how it is changing with a warming climate. We present results of permafrost research from Villum Research Station at Station Nord, the northernmost permafrost monitoring site in Greenland and second northernmost worldwide. We collected core samples from two different 20‐m deep boreholes and measured temperature in the boreholes for over seven years to understand the permafrost's physical and thermal properties, and how the permafrost reacts to the weather and climate. The permafrost began to form more than 8,000 years ago, after the study area was deglaciated and the sea level lowered. A major reason this permafrost is warmer than other sites in the high Arctic is because the area has more than 1 m of snow in the winter, which is unusual for the polar tundra and acts as an insulating layer. Permafrost at 20 m depth has warmed 0.05–0.07°C per year from 2014 to 2021; these rates are similar to those at other high Arctic sites. Key Points: The presented permafrost thermal record is the second northernmost in the Arctic and reveals the warmest known permafrost north of 80°NThe warming rate at 20 m depth was 0.07°C/year and 0.05°C/year at the two sites from 2014 to 2021 despite thick and long‐lasting snow coverEpigenetic permafrost grew into sands and gravels deposited during deglaciation and isostatic emergence of the Prinsesse Ingeborg Halvø [ABSTRACT FROM AUTHOR]

Most climate models neglect cloud longwave (LW) scattering because scattering is considered negligible compared to strong LW absorption by clouds and greenhouse gases. While this rationale is valid for simulating extrapolar regions, it is questionable for the polar regions, where the atmosphere is dry and hence has weak absorption, and ice clouds that have strong scattering capability frequently occur. Using the slab‐ocean Community Earth System Model, we show that ice cloud LW scattering can warm winter surface air temperature by 0.8–1.8 K in the Arctic and 1.3–1.9 K in the Antarctic, while this warming becomes much weaker in polar summer. Such scattering effect cannot be correctly assessed when sea surface temperature and sea ice are prescribed as this effect is manifested through a surface‐atmosphere coupling. Cloud LW scattering is a necessity for the correct simulation of polar climate and surface radiation budget, especially in the winter. Plain Language Summary: Cloud longwave scattering has never been deemed as a necessity in climate models. Out of all climate models in the IPCC fifth and sixth assessments, only three modeling centers have longwave scattering included in their models. Our study explained why the traditional wisdom of neglecting longwave scattering breaks down for the simulation of high‐latitude climate in the fully coupled models. We showed the critical importance of atmosphere‐surface radiative coupling for correctly assessing the role of cloud longwave scattering in the model simulation of climate mean state as well as climate changes, an issue overlooked by all previous studies. We argued that the cloud longwave scattering is a necessity in climate models, not an option. Key Points: Cloud longwave scattering is more important in the polar regions than the extrapolar regionsBy surface‐atmosphere radiative coupling, cloud longwave scattering can warm the polar surface, more in the winter than in the summerCloud longwave scattering is a necessity instead of an option for correctly simulating polar climate and surface energy budget [ABSTRACT FROM AUTHOR]

Snow accumulation and associated synoptic conditions in the Russian Arctic are analysed based on snow depth data from 1950 to 2013 from the All-Russian Research Institute of Hydrometeorological Information—World Data Centre data set. The mean duration of snow coverage in the Russian Arctic is approximately eight to nine months. While the period of snowmelt is usually very short (one or two months), snow accumulates during most of the cold season (October–May). Snow accumulation is associated with negative anomalies of sea level pressure and positive anomalies of air temperature, which means increased cyclonic activity over the analysed region. The cyclones differ in intensity and localization, depending on the area of snowfall. In the western part of the Russian Arctic the cyclones and air masses that bring snowfall may originate from the North Atlantic, while in the eastern part they originate from the Bering Sea, Okhotsk Sea or the North Pacific. The cyclones that bring snowfall may also form locally along the zonal border between two different air masses: the very cold, polar, continental air originating from the Siberian High and the Arctic air from the north, which is often warmer and always more humid than the continental air. [ABSTRACT FROM AUTHOR]