Here we evaluate five atmospheric reanalyses in an Arctic gateway during late summer. The reanalyses include ERA5, ERA‐Interim, Japanese 55 year Re‐Analysis (JRA‐55), Climate Forecasting System ...Reanalysis‐version 2 (CFSv2), and Modern Era Retrospective analysis for Research and Applications‐version 2 (MERRA‐2). We use observations from 50 radiosondes launched in the Fram Strait around 79‐80°N, between 25 August and 11 September 2017. Crucially, data from 27 radiosondes were not transmitted to the Global Telecommunications System and therefore not assimilated into any reanalysis. In most reanalyses, the magnitude of wind speed and humidity errors is similar for profiles with and without data assimilation. In cases without data assimilation, correlation coefficients (R) exceed 0.88 for temperature, wind speed, and specific humidity, in all reanalyses. Overall, the newly released ERA5 has higher correlation coefficients than any other reanalyses as well as smaller biases and root‐mean‐square errors, for all three variables. The largest improvements identified in ERA5 are in its representation of the wind field, and temperature profiles over warm water.
Plain Language Summary
The Arctic is undergoing rapid and ongoing changes. However, due to the harsh environment, there are relatively few observations from this region. To understand the drivers of these changes, we rely heavily on atmospheric reanalyses. Reanalyses are our best guess at the state of the atmosphere at a given time. Reanalyses are generated by assimilating all available atmospheric observations into a weather forecast model. A key question within the scientific community is how accurate reanalyses are in the Arctic. One problem with answering this question is that most observations used to test the performance of reanalyses were ingested in to the model and are therefore not an independent data set. Here we present a new set of balloon‐borne atmospheric observations from the Fram Strait, between Svalbard and Greenland. Many of these data were not assimilated in to any reanalyses, providing a rare opportunity to evaluate their performance in this important Arctic gateway. We test five products, including the newly released ERA5 from the European Centre for Medium Ranged Weather Forecasting. All products simulate the temperature, humidity, and wind fields well, even without data assimilation. Overall, the newly released ERA5 performs best, with the largest improvements in the wind and temperature fields.
Key Points
In situ Arctic observations: 27 atmospheric profiles from radiosondes in Fram Strait (August–Septmber 2017) were not transmitted to GTS
ERA5 simulates observed atmospheric profiles more accurately than ERA‐Interim, JRA‐55, CFSv2, and MERRA‐2
Largest improvements are found in ERA5 for wind and temperature profiles over warmer eastern Fram Strait
Near‐surface air temperatures close to 0°C were observed in situ over sea ice in the central Arctic during the last three winter seasons. Here we use in situ winter (December–March) temperature ...observations, such as those from Soviet North Pole drifting stations and ocean buoys, to determine how common Arctic winter warming events are. Observations of winter warming events exist over most of the Arctic Basin. Temperatures exceeding −5°C were observed during >30% of winters from 1954 to 2010 by North Pole drifting stations or ocean buoys. Using the ERA‐Interim record (1979–2016), we show that the North Pole (NP) region typically experiences 10 warming events (T2m > −10°C) per winter, compared with only five in the Pacific Central Arctic (PCA). There is a positive trend in the overall duration of winter warming events for both the NP region (4.25 days/decade) and PCA (1.16 days/decade), due to an increased number of events of longer duration.
Plain Language Summary
During the last three winter seasons, extreme warming events were observed over sea ice in the central Arctic Ocean. Each of these warming events were associated with temperatures close to or above 0°C, which lasted for between 1 and 3 days. Typically temperatures in the Arctic at this time of year are below −30°C. Here we study past temperature observations in the Arctic to investigate how common winter warming events are. We use time temperature observations from expeditions such as Fram (1893–1896) and manned Soviet North Pole drifting ice stations from 1937 to 1991. These historic temperature records show that winter warming events have been observed over most of the Arctic Ocean. Despite a thin network of observation sites, winter time temperatures above −5°C were directly observed approximately once every 3 years in the central Arctic Ocean between 1954 and 2010. Winter warming events are associated with storm systems originating in either the Atlantic or Pacific Oceans. Twice as many warming events originate from the Atlantic Ocean compared with the Pacific. These storms often penetrate across the North Pole. While observations of winter warming events date back to 1896, we find an increasing number of winter warming events in recent years.
Key Points
Arctic winter warming events are a normal part of the Arctic winter climate. Observations of these events date back to the Fram expedition
North Pole region typically experiences 10 distinct warming events per winter, compared with 5 in the Pacific Central Arctic
Positive trends in the number and duration of Arctic winter warming events (1980–2016), with strongest trends for North Pole domain
Atmospheric measurements were made over Arctic sea ice north of Svalbard from winter to early summer (January–June) 2015 during the Norwegian Young Sea Ice (N‐ICE2015) expedition. These measurements, ...which are available publicly, represent a comprehensive meteorological data set covering the seasonal transition in the Arctic Basin over the new, thinner sea ice regime. Winter was characterized by a succession of storms that produced short‐lived (less than 48 h) temperature increases of 20 to 30 K at the surface. These storms were driven by the hemispheric scale circulation pattern with a large meridional component of the polar jet stream steering North Atlantic storms into the high Arctic. Nonstorm periods during winter were characterized by strong surface temperature inversions due to strong radiative cooling (“radiatively clear state”). The strength and depth of these inversions were similar to those during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. In contrast, atmospheric profiles during the “opaquely cloudy state” were different to those from SHEBA due to differences in the synoptic conditions and location within the ice pack. Storm events observed during spring/summer were the result of synoptic systems located in the Barents Sea and the Arctic Basin rather than passing directly over N‐ICE2015. These synoptic systems were driven by a large‐scale circulation pattern typical of recent years, with an Arctic Dipole pattern developing during June. Surface temperatures became near‐constant 0°C on 1 June marking the beginning of summer. Atmospheric profiles during the spring and early summer show persistent lifted temperature and moisture inversions that are indicative of clouds and cloud processes.
Key Points
Analysis of a new comprehensive meteorological data set over Arctic sea ice from winter to summer
Measurements of Arctic storms during winter show large but short‐lived impact on atmospheric temperature
Spring/summer atmosphere is characterized by persistent temperature and humidity inversions indicative of clouds
The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One ...critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms beneath ponded sea ice during summer, indicating that satellite-based Arctic annual primary production estimates may be significantly underestimated. Here we present a unique time-series of a phytoplankton spring bloom observed beneath snow-covered Arctic pack ice. The bloom, dominated by the haptophyte algae Phaeocystis pouchetii, caused near depletion of the surface nitrate inventory and a decline in dissolved inorganic carbon by 16 ± 6 g C m
. Ocean circulation characteristics in the area indicated that the bloom developed in situ despite the snow-covered sea ice. Leads in the dynamic ice cover provided added sunlight necessary to initiate and sustain the bloom. Phytoplankton blooms beneath snow-covered ice might become more common and widespread in the future Arctic Ocean with frequent lead formation due to thinner and more dynamic sea ice despite projected increases in high-Arctic snowfall. This could alter productivity, marine food webs and carbon sequestration in the Arctic Ocean.
This study evaluates the performance of six atmospheric reanalyses (ERA-Interim, ERA5, JRA-55, CFSv2, MERRA-2, and ASRv2) over Arctic sea ice from winter to early summer. The reanalyses are evaluated ...using observations from the Norwegian Young Sea Ice campaign (N-ICE2015), a 5-month ice drift in pack ice north of Svalbard. N-ICE2015 observations include surface meteorology, vertical profiles from radiosondes, as well as radiative and turbulent heat fluxes. The reanalyses simulate surface analysis variables well throughout the campaign, but have difficulties with most forecast variables. Wintertime (January–March) correlation coefficients between the reanalyses and observations are above 0.90 for the surface pressure, 2-m temperature, total column water vapor, and downward longwave flux. However, all reanalyses have a positive wintertime 2-m temperature bias, ranging from 1° to 4°C, and negative (i.e., upward) net longwave bias of 3–19 W m−2. These biases are associated with poorly represented surface inversions and are largest during cold-stable periods. Notably, the recent ERA5 and ASRv2 datasets have some of the largest temperature and net longwave biases, respectively. During spring (April–May), reanalyses fail to simulate observed persistent cloud layers. Therefore they overestimate the net shortwave flux (5–79 W m−2) and underestimate the net longwave flux (8–38 W m−2). Promisingly, ERA5 provides the best estimates of downward radiative fluxes in spring and summer, suggesting improved forecasting of Arctic cloud cover. All reanalyses exhibit large negative (upward) residual heat flux biases during winter, and positive (downward) biases during summer. Turbulent heat fluxes over sea ice are simulated poorly in all seasons.
During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ...ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.
Winter time atmospheric observations from the 2015 Norwegian young sea‐ICE campaign (N‐ICE2015) are compared with data from the 1997–1998 Surface Heat Budget of the Arctic (SHEBA) campaign. Both data ...sets have a bimodal distribution of the net longwave radiative flux for January–February, with modal values of −40 W m−2 and 0 W m−2. These values correspond to the radiatively clear and opaquely cloudy states, respectively, and are likely to be representative of the wider Arctic. The new N‐ICE2015 observations demonstrate that the two winter states operate in the Atlantic sector of the Arctic and regions of thin sea ice. We compare the N‐ICE2015 and SHEBA data with ERA‐Interim and output from the coupled Arctic regional climate model HIRHAM‐NAOSIM. ERA‐Interim simulates two Arctic winter states well and captures the timing of transitions from one state to the other, despite underestimating the cloud liquid water path. HIRHAM‐NAOSIM has more cloud liquid water compared with ERA‐Interim but simulates the two states poorly. Our results demonstrate that models must simulate realistic synoptic forcing and temperature profiles to accurately capture the two Arctic winter states, and not only the presence of mixed‐phase clouds. Using ERA‐Interim, we find a positive trend in the number of opaquely cloudy days in the western Atlantic sector of the Arctic, and a strong correlation with the mean winter temperature over much of the Arctic Basin. Hence, the two Arctic winter states are important for understanding interannual variability in the Arctic. The N‐ICE2015 data set will help improve our understanding of these relationships.
Key Points
Two Arctic winter states are observed during the N‐ICE2015 and SHEBA campaigns with similar net longwave fluxes
ERA‐Interim captures the transitions from radiatively clear to opaquely cloudy states during N‐ICE2015 and SHEBA
Strong correlation between number of opaquely cloudy days and mean winter temperature over large areas of the Arctic
A simple method for estimating the global radiative forcing caused by the sea ice–albedo feedback in the Arctic is presented. It is based on observations of cloud cover, sea ice concentration, and ...top‐of‐atmosphere broadband albedo. The method does not rely on any sort of climate model, making the assumptions and approximations clearly visible and understandable and allowing them to be easily changed. Results show that the globally and annually averaged radiative forcing caused by the observed loss of sea ice in the Arctic between 1979 and 2007 is approximately 0.1 W m−2; a complete removal of Arctic sea ice results in a forcing of about 0.7 W m−2, while a more realistic ice‐free summer scenario (no ice for 1 month and decreased ice at all other times of the year) results in a forcing of about 0.3 W m−2, similar to present‐day anthropogenic forcing caused by halocarbons. The potential for changes in cloud cover as a result of the changes in sea ice makes the evaluation of the actual forcing that may be realized quite uncertain since such changes could overwhelm the forcing caused by the sea ice loss itself, if the cloudiness increases in the summertime.
Key Points
The radiative forcing due to sea ice loss can be simply calculated
Current forcing is small, around 0.1 W/m2; it could increase to about 0.3 W/m2
Better understanding of related cloud changes is critical for full understanding
•Synthetic fentanyls are almost always detected in cases where there is misuse of heroin.•Carfentanil is reported as being 10,000 times more potent than morphine.•Standard toxicology screens do not ...always detect the low concentrations of synthetic fentanyls.•Synthetic fentanyls must be tested for in drug deaths where other drug concentrations are low.
Synthetic fentanyl analogues are highly potent opioid drugs which have no pharmaceutical use in humans. We detected the synthetic fentanyl analogues; carfentanil, butyryl fentanyl, fluorobutyrylfentanyl, furanylfentanyl, and alfentanil as well as fentanyl itself in 25 cases in early 2017. There have been no previous reports of synthetic fentanyl deaths in the United Kingdom (UK).
Cases in which the history clearly stated drug use but where a post mortem blood morphine concentration was lower than would be expected to explain the sudden death, were referred for further analysis by high resolution accurate mass (HRAM) mass spectrometry.
25 post mortem cases in which synthetic fentanyl analogues were implicated in the cause of death were reported from January to May 2017. No cases were seen in June 2017. The age range was 21–54 years and 22 were male. There was a history of heroin use, or markers of heroin use on toxicology screening in 21/25 cases. Carfentanil and fentanyl were detected in 7 cases. Multiple synthetic fentanyl analogues were present in 13 cases, with the remaining 5 cases having only carfentanil present. Synthetic fentanyl analogues were detected in combination with other drugs in all cases. Significant concentrations of ethanol were detected in only 2 cases. The concentration range of carfentanil in blood was 90–4004pg/mL. Of note, the 3 cases in which ante mortem carfentanil was quantified ranged from 21 to 98pg/mL. In all cases, death was attributed to combined central nervous system depression.
This paper highlights a new and rapid emergence of these drugs into the UK illicit drug arena. Synthetic fentanyl analogues represent a significant challenge both analytically and clinically within the groups who misuse drugs. It is worthwhile considering the possibility of the presence of these drugs in cases in which a toxicological cause of death is not apparent analytically but there is a history of drug use and circumstantial evidence exists to support a drug-related death as the most likely cause. It may be that synthetic fentanyl analogues should be screened for routinely to avoid reporting any false negative results, but the cost implications and viability of this have not been fully evaluated.
We examine the relative effect of warming events (storms) and snow cover on thermodynamic growth of Arctic sea ice in winter. We use a 1-D snow and ice thermodynamic model to perform sensitivity ...experiments. Observations from the winter period of the Norwegian young sea ICE (N-ICE2015) campaign north of Svalbard are used to initiate and force the model. The N-ICE2015 winter was characterized by frequent storm events that brought pulses of heat and moisture, and a thick snow cover atop the sea ice (0.3–0.5 m). By the end of the winter, sea-ice bottom growth was negligible. We show that the thermodynamic effect of storms to the winter sea-ice growth is controlled by the amount of snow on sea ice. For 1.3 m initial ice thickness, the decrease in ice growth caused by the warming events ranged from −1.4% (for 0.5 m of snow) to −7.5% (for snow-free conditions). The decrease in sea-ice growth caused by the thick snow (0.5 m) was more important, ranging from −17% (with storms) to −23% (without storms). The results showcase the critical role of snow on winter Arctic sea-ice growth.
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