Assessment of Greenland surface melt algorithms based on DMSP and SMOS data

Satellite-borne microwave radiometers provide essential measurements to study the surface melt state of ice sheets. Therefore, selecting suitable microwave radiometer data is critical to characterize the spatial distribution of surface melt. In this study, we investigated the Greenland Ice Sheet and evaluated the usefulness, as climate indicators, of data acquired by microwave radiometers onboard the F17 satellite of the United States of America Defense Meteorological Satellite Program(DMSP) and the Soil Moisture and Ocean Salinity(SMOS) satellite of the European Space Agency. First, surface melt was simulated using the DMSP dataset as input for a brightness temperature threshold algorithm, the Microwave Emission Model of Layered Snowpacks(MEMLS2), and the SMOS dataset as input for the L-band Specific MEMLS(LS-MEMLS). For accuracy evaluation, the simulation results were then compared with surface melt estimates derived from air temperature measurements at Automatic Weather Stations and from ice surface temperature measurements from the Moderate Resolution Imaging Spectroradiometer(MODIS) satellite-borne instrument. Our results show that global(over Greenland) MEMLS2 simulation performance(overall accuracy 83%) was higher than that of LS-MEMLS(overall accuracy 78%). However, in southeastern Greenland, MEMLS2 omission error was markedly higher than that of LS-MEMLS, whereas LS-MEMLS could detect longer-lasting surface melt than MEMLS2. This analysis showed that DMSP-based surface melt simulations are more accurate than SMOS-based simulations, thereby providing a data selection reference for surface melt studies of the Greenland Ice Sheet.

Analysis of the record-breaking August 2021 rainfall over the Greenland Ice Sheet

Rainfall was witnessed for the first time at the highest area of the Greenland Ice Sheet on 14 August,2021.The thermodynamic mechanisms supporting the rainfall are revealed by ERA5 reanalysis,in-situ and satellite data.We find that a strong southward intrusion of the polar vortex favored the maintenance of a deep cyclone over Baffin Island and an amplification of anticyclonic circulation over the southeastern ice sheet,which pumped warm and moist air toward Greenland from anomalously warm waters south of Greenland.Across a wide swath of the ice sheet,atmospheric uplift maintained above-melting and rainfall conditions via condensation and enhanced downward infrared irradiance.Without the low-level liquid clouds,the spatial extent and duration of the rainfall would have been smaller.Over the ice sheet topographic summit,the air temperature from the ground to 250 hPa level was~2℃higher than the previous record set on 12 July,2012.Such events may occur more frequently with the decreased temperature contrast between the Arctic and the mid-latitude regions that drives highly amplified jet streams.Thus,this extreme event serves as a harbinger of a more likely wet surface condition across all elevations of the ice sheet.

Vibrocorer for undisturbed sampling of firn aquifer layers in Greenland: general concept

The firn aquifer beneath the Greenland Ice Sheet may play a significant role in rising sea level. Both traditional mechanical drilling and electric thermal drilling are poorly adapted for effective, low-disturbance sampling in firn aquifers. We propose using a vibrocoring technique for the undisturbed sampling of dry firn and firn aquifer layers. A remote-controlled vibrocorer is designed to obtain 1-m-long cores with a diameter of 100 mm. The depth capacity of the system is approximately 50 m. The total weight of the vibrocoring system with the surface auxiliary equipment is approximately 110 kg, and corer assembly itself weighs ~60 kg.

Persistently explore new understandings of Greenland Ice Sheet ablation

Greenland and Antarctic ice sheets are the largest potential contributors to global sea level rise(GSLR),amounting to more than 64 m of sea level equivalence(SLE).Between the two,Greenland Ice Sheet(GrIS)alone comprises about 7 mSLE,with a much faster speed of ablation than the Antarctic Ice Sheet.

Performance of surface radiation products of Greenland Ice Sheet using in-situ measurements

Radiation is the direct energy source of the surface natural environment and the main driving force of climate change.It has increasingly become an important meteorological factor affecting the surface heat exchange and glacier mass balance,especially in the glacier changes of the Greenland Ice Sheet(Gr IS).Due to the harsh climatic conditions of Gr IS and sparse observed data,it has become an important way to obtain radiation data from reanalysis datasets.However,the applicability of these radiation data on Gr IS is uncertain and worth exploring.In this work,we evaluate five reanalysis datasets(the fifth generation of European Centre for Medium-Range Weather Forecasts(ERA5),European Centre for Medium-Range Weather Forecasts Interim Reanalysis(ERA-Interim),Japanese 55-year Reanalysis(JRA55),National Centers for Environmental Prediction Reanalysis II(NCEP2)and Modern-Era Retrospective analysis for Research and Applications,Version 2(MERRA-2))during 1997-2022 using observations from 26 Program for Monitoring the Greenland Ice Sheet(PROMICE)automatic weather stations(AWSs)and 3 K-transect AWSs on Gr IS.The conclusions are as follows:ERA5 has the best performances in downward shortwave radiation(SWD)as well as downward and upward longwave radiation(LWD and LWU),but the performance is not the best in upward shortwave radiation(SWU).Based on the radiation budget analysis with ERA5 during 1979-2022,the fluctuation of longwave radiation is greater than that of shortwave radiation.The seasonal variation of shortwave radiation is obvious,while that of longwave radiation is small.The increasing trend of longwave radiation may result from global warming,in which ice sheets absorb more solar radiation and the surface heats up significantly,emitting more LWU.

The Relationship between the Wintertime Blocking over Greenland and the Sea Ice Distribution over North Atlantic

The sea-ice concentration in the Northern Hemisphere, 500 hPa height, sea-level pressure and 1000-500 hPa thickness of monthly mean data are examined for the period 1953-1989, with emphasis on the winter season.Relationships between large-scale patterns of atmospheric variability and sea-ice variability are investigated, making use of the correlation method. The analysis is conducted for the Atlantic sectors. In agreement with earlier studies based upon monthly mean data on sea-ice concentration, the strongest sea-ice pattern is composed of a dipole with opposing centers of action in the Davis Straits / Labrador Sea region and the Greenland and Barents Seas. Its temporal variability is strongly coupled to the atmospheric North Atlantic Oscillation (NAO). The relationship between the two patterns is strongest with the atmosphere leading the ocean. The polarity of the NAO is associated with Greenland blocking episodes, during which the influence of the atmosphere is strong enough to temporarily halt the

Characterization of the unprecedented polynya events north of Greenland in 2017/2018 using remote sensing and reanalysis data

Based on an ice concentration threshold of 90%,it has been identified that two polynya events occurred in the region north of Greenland during the 2017/2018 ice season.The winter event lasted from February 20 to March 3,2018 and the summer event persisted from August 2 to September 5,2018.The minimum ice concentration derived from Advanced Microwave Scanning Radiometer 2(AMSR2)observations was 72%and 65%during the winter and summer events,respectively.The occurrence of both events can be related to strengthened southerly winds associated with an increased east-west zonal surface level air pressure gradient across the north Greenland due to perturbation of mid-troposphere polar vortex.The relatively warm air temperature during the 2017/2018 freezing season in comparison with previous years,together with the occurrence of the winter polynya,formed favourable pre-conditions for ice field fracturing in summer,which promoted the formation of the summer polynya.Diminished southerly winds and increased cover of new ice over the open water were the dominant factors for the disappearance of the winter polynya,whereas increased ice inflow from the north was the primary factor behind the closure of the summer polynya.Sentinel-1 Synthetic Aperture Radar(SAR)images were found better suited than AMSR2 observations for quantification of a new ice product during the polynya event because the SAR images have high potential for mapping of different sea ice regimes with finely spatial resolution.The unprecedented polynya events north of Greenland in 2017/2018 are important from the perspective of Arctic sea ice loss because they occurred in a region that could potentially be the last“Arctic sea ice refuge”in future summers.

Evaluation of vertical crustal movements and sea level changes around Greenland from GPS and tide gauge observations

To better monitor the vertical crustal movements and sea level changes around Greenland,multiple data sources were used in this paper,including global positioning system(GPS),tide gauge,satellite gravimetry,satellite altimetry,glacial isostatic adjustment(GIA).First,the observations of more than 50 GPS stations from the international GNSS service(IGS)and Greenland network(GNET)in 2007–2018 were processed and the common mode error(CME)was eliminated with using the principal component analysis(PCA).The results show that all GPS stations show an uplift trend and the stations in southern Greenland have a higher vertical speed.Second,by deducting the influence of GIA,the impact of current Gr IS mass changes on GPS stations was analysed,and the GIA-corrected vertical velocity of the GPS is in good agreement with the vertical velocity obtained by gravity recovery and climate experiment(GRACE).Third,the absolute sea level change around Greenland at 4 gauge stations was obtained by combining relative sea level derived from tide gauge observations and crustal uplift rates derived from GPS observations,and was validated by sea level products of satellite altimetry.The results show that although the mass loss of Gr IS can cause considerable global sea level rise,eustatic movements along the coasts of Greenland are quite complex under different mechanisms of sea level changes.

Chinese investment in Greenland

In 2009 Greenland moved to a more extensive degree of self-government in relation to the Kingdom of Denmark(the Realm),and most policy areas related to business activities and investment are now under the control of Greenland.Under the Self-Government Act,Greenland has issued legislation within several business sectors and other business-related policy areas,including the mineral resources sector.Today,Greenland is highly dependent on fishing and fish exports;however,the government is quite ambi-tious in its desire to develop new business sectors and attract foreign investment,including investment from China,especially to develop its mineral resources.China is now the second largest economy in the world,and outbound investments by Chinese companies present unprecedented opportunities for both the Chinese companies and their global partners.However,Chinese outbound investment faces many hurdles,both at home and elsewhere.It is highly advisable for Chinese companies to evaluate the regulatory,political,environmental,labor,and financial conditions and under-stand what remedies may mitigate the risks they identify before investing in Green land.This paper investigates and analyzes the hurdles faced by Chinese investors in both Greenland and the Danish Realm.The paper focuses on but is not limited to investments in the mining industry.

Ground-based GPS Used in the Snow Depth Survey of Greenland

Snow cover is one of the important components of land cover,and it is necessary to accurately monitor the depth and coverage of snow cover.Using the GPS signal receiver data and the basic principle of snow depth detection based on GPS-MR technology,the snow depth of the three sites on the Greenland PBO network GLS1,GLS2,and GLS3 from 2012 to 2018 was obtained.The inversion snow depth is affected by site drift,which is a quite difference from the measured snow depth.Combined with the stable reference point,the velocity field distribution of Greenland Island and the U-direction component change value of the station can be obtained through GAMIT calculation.By analyzing the glacial flow and U-direction component,the influence of the site drift on the snow depth was deducted,and finally compared the corrected inversion snow depth and measured snow depth found that the two were better than before the correction,the results were significantly improved,and the consistency was good.The analysis of the experimental results showed that in extremely cold areas such as Greenland Island,affected by glaciers,the continuous,real-time,high-time resolution snow depth around the measured station obtained by ground-based GPS tracking stations has a large gap with the measured snow depth value,and the gap will gradually increase with time.By deducting the impact of glacier drift,the trend of the two is the same and the consistency is good.The correctness and feasibility of the application of ground-based GPS snow cover theory in the polar area further expand the application scope and practical value of ground-based GPS in snow monitoring.

Hepatitis B among Inuit: A review with focus on Greenland Inuit

Hepatitis B virus(HBV) infection is a disease with a highly variable course. Chronic HBV infection may cause end-stage liver disease including cirrhosis and hepatocellular carcinoma, which is the 3rd most common cause of cancer related death due to the poor prognosis. The prevalence of HBV infection is low in many countries. Still, it remains important due to the potential consequences of the disease. HBV is endemic in the Arctic with serologic markers of chronic HBV infection in up to 29% of the population in some areas in Greenland. Interestingly, Inuit populations rarely show signs of liver disease despite the fact that around half of all Inuit has been exposed to HBV and around 8% of Inuit are chronically infected with HBV. These findings have been consistent in surveys conducted for more than four decades among Arctic Inuit. We thus review HBV infection in the Arctic with focus on Greenland Inuit and compared with Inuit in Canada, Alaska and Siberia. The aspects described include epidemiology and monitoring of the disease, as well as treatment and the risk of liver cancer.

Vertical Chlorophyll and Dimethylsulfide Profile Simulations in Southern Greenland Sea

Biogenetic sulfide dimethylsulfide(DMS)plays a major role on the global climate,especially in Arctic Ocean.Accurate simulate DMS concentration is an important task.Here we introduced both biogeochemical depth-averaged model G93 and its extension model-one dimensional DMS model.Both surface concentrations,vertical profiles of chlorophyll(CHL)and DMS are simulated using the two models within southern Greenland Sea(0°E–10°E,70°N–75°N)during year 2012.As the input data for the models simulations,the spatial monthly mean of methodology forcings including sea surface temperature(SST),wind speed(WIND),cloud cover(CLD),sea ice concentration(ICE)and mixed layer depth(MLD)are calculated.Satellite 8-day time series of chlorophyll-a(CHL)are used as observation data for CHL related parameter calibrations.Simó’s imperial formula is used as the monthly DMS observation data.The Genetic Algorithm technique is used for the parameter calibrations.The simulation results show that the most DMS related surface concentrations exhibit the normal distributions with peak during May.CHL,DMS and DMSP(dimethylsulphoniopropionate)vertical profiles are obtained for July,August and September in year 2012.CHL had the higher variation of subsurface concentration maximum(SCM)in July with the lower surface concentration value.DMS had surface higher and subsurface lower profile for the all three months.DMSP also had subsurface high in July.The SCM CHL diurnal variation in the subsurface also can be resulted from diurnal changes in MLD and vertical mixing variations,plus photolysis and wind-driven ventilations.

Considerable increase in bowhead,blue,humpback and fin whales numbers in the Greenland Sea and Fram Strait between 1979 and 2014

In the frame of our long-term study of cetacean abundance and distribution in polar marine ecosystems begun in1979,a drastic increase in the bowhead Balaena mysticetus North Atlantic "stock" was observed from 2005 on,by a factor 30 and more:from 0.0002 per count between 1979 and 2003(one individual,n=5430 counts) to 0.06 per count from 2005 to 2014(34 individuals,n=6000 counts);the most significant part of the increase occurred from 2007 on.Other large whale species(Mysticeti) showed a similar pattern,mainly blue Balaenoptera musculus,humpback Megaptera novaeangliae and fin whales Balaenoptera physalus.This large and abrupt increase cannot logically be due to population growth,nor to survival of a hidden "relic" population,nor to a changing geographical distribution within the European Arctic,taking into account the importance of the coverage during this study.Our interpretation is that individuals passed through the Northwest and/or Northeast Passages from the larger Pacific stock into the almost depleted North Atlantic populations coinciding with a period of very low ice coverage—at the time the lowest ever recorded.In contrast,no clear evolution was detected neither for sperm whale Physeter macrocephalus nor for Minke whale Balaenoptera acusrostrata.

Thinner Sea Ice Contribution to the Remarkable Polynya Formation North of Greenland in August 2018

In August 2018,a remarkable polynya was observed off the north coast of Greenland,a perennial ice zone where thick sea ice cover persists.In order to investigate the formation process of this polynya,satellite observations,a coupled iceocean model,ocean profiling data,and atmosphere reanalysis data were applied.We found that the thinnest sea ice cover in August since 1978(mean value of 1.1 m,compared to the average value of 2.8 m during 1978-2017) and the modest southerly wind caused by a positive North Atlantic Oscillation(mean value of 0.82,compared to the climatological value of-0.02) were responsible for the formation and maintenance of this polynya.The opening mechanism of this polynya differs from the one formed in February 2018 in the same area caused by persistent anomalously high wind.Sea ice drift patterns have become more responsive to the atmospheric forcing due to thinning of sea ice cover in this region.

New U-Pb Ages for Mafic Dykes of SE Greenland

The North Atlantic Craton(NAC)represents one of approximately three dozen preserved Archean cratonic fragments now dispersed globally,but its affinity to formerly neighboring supercontinent cratonic

Climate Change Associated with Global Teleconnections, Volcanic Eruptions, and the Arctic’s Snow-Ice Albedo in Godthab, Greenland

To study the impact of climate change on Godthab(Greenland), temperature and precipitation gathered from the Global Historical Climatology Network (GHCN) were analyzed for patterns within 1866-2011. Both temperature and precipitation have experienced an overall increase throughout the past 146 years. Precipitation, however, has experienced a declining trend since 1985. North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices showed strong correlations with average annual temperature (R = ?0.6) and smaller correlations with annual total precipitation (R = ?0.2). There are moderate correlations between temperature, precipitation, and Southern-Oscillation Index (SOI). The positive phases of Pacific-North American (PNA) led to increased winter and spring precipitation. The climate mode’s influential strength on Godthab’s temperature and precipitation, vary seasonally. In contrast with global average temperatures, Greenland has not experienced a continual warming trend since the 1950s;30- and 10-year trends show a cooling period between 1965 and 1995. From 1866 to 2011, Godthab’s average annual temperature has increased by 1.9?C, and is anticipated to continue to warm in accordance with the global warming trend and the Arctic’s associated feedback mechanisms.

China Housing Industry Association under the All-China Federation of Industry and Commerce has now launched its Sustainable Asia-Pacific Greenland Brand

This community of townhouses in Chengdu, SichuanProvince was developed by Dalian’s Wanda Group

Accumulation over the Greenland Ice Sheet as Represented in Reanalysis Data

Annual precipitation,evaporation,and calculated accumulation from reanalysis model outputs have been investigated for the Greenland Ice Sheet (GrIS),based on the common period of 1989-2001.The ERA-40 and ERA-interim reanalysis data showed better agreement with observations than do NCEP-1 and NCEP-2 reanalyses.Further,ERA-interim showed the closest spatial distribution of accumulation to the observation.Concerning temporal variations,ERA-interim showed the best correlation with precipitation observations at five synoptic stations,and the best correlation with in situ measurements of accumulation at nine ice core sites.The mean annual precipitation averaged over the whole GrIS from ERA-interim (363 mm yr 1) and mean annual accumulation (319 mm yr 1) are very close to the observations.The validation of accumulation calculated from reanalysis data against ice-core measurements suggests that further improvements to reanalysis models are needed.

Greenland Ice Sheet Contribution to Future Global Sea Level Rise based on CMIP5 Models

Sea level rise(SLR) is one of the major socioeconomic risks associated with global warming. Mass losses from the Greenland ice sheet(GrIS) will be partially responsible for future SLR, although there are large uncertainties in modeled climate and ice sheet behavior. We used the ice sheet model SICOPOLIS(SImulation COde for POLythermal Ice Sheets) driven by climate projections from 20 models in the fifth phase of the Coupled Model Intercomparison Project(CMIP5) to estimate the GrIS contribution to global SLR. Based on the outputs of the 20 models, it is estimated that the GrIS will contribute 0–16(0–27) cm to global SLR by 2100 under the Representative Concentration Pathways(RCP) 4.5(RCP 8.5) scenarios. The projected SLR increases further to 7–22(7–33) cm with 2×basal sliding included. In response to the results of the multimodel ensemble mean, the ice sheet model projects a global SLR of 3 cm and 7 cm(10 cm and 13 cm with 2×basal sliding) under the RCP 4.5 and RCP 8.5 scenarios, respectively. In addition, our results suggest that the uncertainty in future sea level projection caused by the large spread in climate projections could be reduced with model-evaluation and the selective use of model outputs.

The relationships among aerosol optical depth, ice, phytoplankton and dimethylsulfide and the implication for future climate in the Greenland Sea

The sea-to-air flux of dimethylsulphide(DMS) is one of the major sources of marine biogenic aerosol, and can have an important radiative impact on climate, especially in the Arctic Ocean. Satellite-derived aerosol optical depth(AOD) is used as a proxy for aerosol burden which is dominated by biogenic aerosol during summer and autumn. The spring sea ice melt period is a strong source of aerosol precursors in the Arctic. However, high aerosol levels in early spring are likely related to advection of continental pollution from the south(Arctic haze).Higher AOD was generally registered in the southern part of the study region. Sea ice concentration(SIC) and AOD were positively correlated, while cloud cover(CLD) and AOD were negative correlation. The seasonal peaks of SIC and CLD were both one month ahead of the peak in AOD. There is a strong positive correlation between AOD and SIC. Melting ice is positively correlated with chlorophyll a(CHL) almost through March to September,but negatively correlated with AOD in spring and early summer. Elevated spring and early summer AOD most likely were influenced by combination of melting ice and higher spring wind in the region. The peak of DMS flux occurred in spring due to the elevated spring wind and more melting ice. DMS concentration and AOD were positively correlated with melting ice from March to May. Elevated AOD in early autumn was likely related to the emission of biogenic aerosols associated with phytoplankton synthesis of DMS. The DMS flux would increase more than triple by 2100 in the Greenland Sea. The significant increase of biogenic aerosols could offset the warming in the Greenland Sea.