Evidence for Elevation-Dependent Warming in the St. Elias Mountains, Yukon, Canada

AbstractThe climate of high midlatitude mountains appears to be warming faster than the global average, but evidence for such elevation-dependent warming (EDW) at higher latitudes is presently scarce. Here, we use a comprehensive network of remote meteorological stations, proximal radiosonde measurements, downscaled temperature reanalysis, ice cores, and climate indices to investigate the manifestation and possible drivers of EDW in the St. Elias Mountains in subarctic Yukon, Canada. Linear trend analysis of comprehensively validated annual downscaled North American Regional Reanalysis (NARR) gridded surface air temperatures for the years 1979–2016 indicates a warming rate of 0.028°C a−1 between 5500 and 6000 m above mean sea level (MSL), which is ~1.6 times larger than the global-average warming rate between 1970 and 2015. The warming rate between 5500 and 6000 m MSL was ~1.5 times greater than the rate at the 2000–2500 m MSL bin (0.019°C a−1), which is similar to the majority of warming rates estimated worldwide over similar elevation gradients. Accelerated warming since 1979, measured by radiosondes, indicates a maximum rate at 400 hPa (~7010 m MSL). EDW in the St. Elias region therefore appears to be driven by recent warming of the free troposphere. MODIS satellite data show no evidence for an enhanced snow albedo feedback above 2500 m MSL, and declining trends in sulfate aerosols deposited in high-elevation ice cores suggest a modest increase in radiative forcing at these elevations. In contrast, increasing trends in water vapor mixing ratio at the 500-hPa level measured by radiosonde suggest that a longwave radiation vapor feedback is contributing to EDW.

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A North American regional reanalysis climatology of the Haines Index

International Journal of Wildland Fire ◽

10.1071/wf08196 ◽

2011 ◽

Vol 20 (1) ◽

pp. 91 ◽

Cited By ~ 11

Author(s):

Wei Lu ◽

Joseph J. Charney ◽

Sharon Zhong ◽

Xindi Bian ◽

Shuhua Liu

Keyword(s):

North America ◽

Linear Trend ◽

Warm Season ◽

High Elevation ◽

Reanalysis Data ◽

Spatial And Temporal Variability ◽

Elevation Gradients ◽

Regional Reanalysis ◽

Sloping Terrain ◽

Lapse Rates

A warm-season (May through October) Haines Index climatology is derived using 32-km regional reanalysis temperature and humidity data from 1980 to 2007. We compute lapse rates, dewpoint depressions, Haines Index factors A and B, and values for each of the low-, mid- and high-elevation variants of the Haines Index. Statistical techniques are used to investigate the spatial and temporal variability of the index across North America. The new climatology is compared with a previous climatology derived from 2.5° (~280 km) global reanalysis data. Maps from the two climatologies are found to be very similar for most of North America. The largest differences appear along the eastern coastline and in regions of large elevation gradients, where the orography in the 32-km climatology is better resolved than that of the 2.5° climatology. In coastal areas of eastern North America and where there is steeply sloping terrain, the new climatology can augment the information from the 2.5° climatology to help analyse the performance and interpret the results of the Haines Index in these regions. A linear trend analysis of the total number of high-Haines Index days occurring in each warm season reveals no significant linear trends over the 28-year data period.

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Improved estimates of preindustrial biomass burning reduce the magnitude of aerosol climate forcing in the Southern Hemisphere

Science Advances ◽

10.1126/sciadv.abc1379 ◽

2021 ◽

Vol 7 (22) ◽

pp. eabc1379

Author(s):

Pengfei Liu ◽

Jed O. Kaplan ◽

Loretta J. Mickley ◽

Yang Li ◽

Nathan J. Chellman ◽

...

Keyword(s):

Southern Hemisphere ◽

Radiative Forcing ◽

Ice Core ◽

Ice Cores ◽

Terrestrial Ecosystems ◽

Rapid Expansion ◽

Past Century ◽

Fire Emissions ◽

The Past ◽

Fire Activity

Fire plays a pivotal role in shaping terrestrial ecosystems and the chemical composition of the atmosphere and thus influences Earth’s climate. The trend and magnitude of fire activity over the past few centuries are controversial, which hinders understanding of preindustrial to present-day aerosol radiative forcing. Here, we present evidence from records of 14 Antarctic ice cores and 1 central Andean ice core, suggesting that historical fire activity in the Southern Hemisphere (SH) exceeded present-day levels. To understand this observation, we use a global fire model to show that overall SH fire emissions could have declined by 30% over the 20th century, possibly because of the rapid expansion of land use for agriculture and animal production in middle to high latitudes. Radiative forcing calculations suggest that the decreasing trend in SH fire emissions over the past century largely compensates for the cooling effect of increasing aerosols from fossil fuel and biofuel sources.

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Linear trend and abrupt changes of climate indices in the arid region of northwestern China

Atmospheric Research ◽

10.1016/j.atmosres.2017.06.008 ◽

2017 ◽

Vol 196 ◽

pp. 108-118 ◽

Cited By ~ 16

Author(s):

Huaijun Wang ◽

Yingping Pan ◽

Yaning Chen ◽

Zhengwei Ye

Keyword(s):

Arid Region ◽

Linear Trend ◽

Northwestern China ◽

Climate Indices ◽

Abrupt Changes

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Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-3751-2014 ◽

2014 ◽

Vol 14 (7) ◽

pp. 3751-3769 ◽

Cited By ~ 21

Author(s):

T. M. Saeed ◽

H. Al-Dashti ◽

C. Spyrou

Keyword(s):

Optical Thickness ◽

Dust Storm ◽

Radiative Forcing ◽

Longwave Radiation ◽

Aerosol Optical Thickness ◽

Radiative Heating ◽

Dust Layer ◽

Surface Level ◽

Maximum Value ◽

Direct Radiative Forcing

Abstract. Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to −0.0234 and −0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude–longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2 and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day−1 between 3 and 5 km, dropped to 1.5 K day−1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day−1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of −0.1 K day−1 at 6 km.

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Instantaneous longwave radiative impact of ozone: an application on IASI/MetOp observations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-21177-2015 ◽

2015 ◽

Vol 15 (15) ◽

pp. 21177-21218

Author(s):

S. Doniki ◽

D. Hurtmans ◽

L. Clarisse ◽

C. Clerbaux ◽

H. M. Worden ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Longwave Radiation ◽

Polar Regions ◽

Direct Integration ◽

Direct Integration Method ◽

Radiative Impact ◽

Ozone Variation ◽

Atmospheric Sounding ◽

Stratospheric Intrusions

Abstract. Ozone is an important greenhouse gas in terms of anthropogenic radiative forcing (RF). RF calculations for ozone were until recently entirely model based and significant discrepancies were reported due to different model characteristics. However, new instantaneous radiative kernels (IRKs) calculated from hyperspectral thermal IR satellites have been able to help adjudicate between different climate model RF calculations. IRKs are defined as the sensitivity of the outgoing longwave radiation (OLR) flux with respect to the ozone vertical distribution in the full 9.6 μm band. Previous methods applied to measurements from the Tropospheric Emission Spectrometer (TES) on Aura, rely on an anisotropy approximation for the angular integration. In this paper, we present a more accurate but more computationally expensive method to calculate these kernels. The method of direct integration is based on similar principles with the anisotropy approximation, but deals more precisely with the integration of the Jacobians. We describe both methods and highlight their differences with respect to the IRKs and the ozone longwave radiative effect (LWRE), i.e. the radiative impact in OLR due to absorption by ozone, for both tropospheric and total columns, from measurements of the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases between the two methods vary from −25 to +20 % for the LWRE, depending on the viewing angle. These biases point to the inadequacy of the anisotropy method, especially at nadir, suggesting that the TES derived LWRE are biased low by around 25 % and that chemistry-climate model OLR biases with respect to TES are underestimated. In this paper we also exploit the sampling performance of IASI to obtain first daily global distributions of the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the direct integration method. We show that the temporal variation of global and latitudinal averages of the LWRE shows patterns which are controlled by changes in the surface temperature and ozone variation due to specific processes, such as the ozone hole in the Polar regions and stratospheric intrusions into the troposphere.

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Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

Nature Communications ◽

10.1038/s41467-021-27642-5 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Juan Pablo Corella ◽

Niccolo Maffezzoli ◽

Andrea Spolaor ◽

Paul Vallelonga ◽

Carlos A. Cuevas ◽

...

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Radiative Forcing ◽

Climate Changes ◽

Ice Cores ◽

The Arctic ◽

Glacial Cycle ◽

Ice Dynamics ◽

Sea Ice Dynamics ◽

Ultrafine Aerosol

AbstractIodine has a significant impact on promoting the formation of new ultrafine aerosol particles and accelerating tropospheric ozone loss, thereby affecting radiative forcing and climate. Therefore, understanding the long-term natural evolution of iodine, and its coupling with climate variability, is key to adequately assess its effect on climate on centennial to millennial timescales. Here, using two Greenland ice cores (NEEM and RECAP), we report the Arctic iodine variability during the last 127,000 years. We find the highest and lowest iodine levels recorded during interglacial and glacial periods, respectively, modulated by ocean bioproductivity and sea ice dynamics. Our sub-decadal resolution measurements reveal that high frequency iodine emission variability occurred in pace with Dansgaard/Oeschger events, highlighting the rapid Arctic ocean-ice-atmosphere iodine exchange response to abrupt climate changes. Finally, we discuss if iodine levels during past warmer-than-present climate phases can serve as analogues of future scenarios under an expected ice-free Arctic Ocean. We argue that the combination of natural biogenic ocean iodine release (boosted by ongoing Arctic warming and sea ice retreat) and anthropogenic ozone-induced iodine emissions may lead to a near future scenario with the highest iodine levels of the last 127,000 years.

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Modelling high-latitude explosive eruptions and their atmospheric and environmental impacts

10.5194/egusphere-egu21-15780 ◽

2021 ◽

Author(s):

Herman Fuglestvedt ◽

Zhihong Zhuo ◽

Michael Sigl ◽

Matthew Toohey ◽

Michael Mills ◽

...

Keyword(s):

Environmental Impacts ◽

High Latitude ◽

Radiative Forcing ◽

General Circulation ◽

Lower Thermosphere ◽

Circulation Model ◽

Ice Cores ◽

Volcanic Eruptions ◽

Explosive Eruptions ◽

Sulphate Deposition

Large explosive volcanic eruptions inject sulphur into the stratosphere where it is converted to sulphur dioxide and sulphate aerosols. Due to atmospheric circulation patterns, aerosols from high-latitude eruptions typically remain concentrated in the hemisphere in which they are injected. Eruptions in the high-latitude Northern Hemisphere could thus lead to a stronger hemispheric radiative forcing and surface climate response than tropical eruptions, a claim that is supported by a previous study based on proxy records and the coupled aerosol-general circulation model MAECHAM5-HAM. Additionally, the subsequent surface deposition of volcanic sulphate is potentially harmful to humans and ecosystems, and an improved understanding of the deposition over polar ice sheets can contribute to better reconstructions of historical volcanic forcing. On this basis, we model Icelandic explosive eruptions in a pre-industrial atmosphere, taking both volcanic sulphur and halogen loading into account. We use the fully coupled Earth system model CESM2 with the atmospheric component WACCM6, which extends to the lower thermosphere and has prognostic stratospheric aerosols and full chemistry. In order to study the volcanic impacts on the atmosphere, environment, and sulphate deposition, we vary eruption parameters such as sulphur and halogen loading, and injection altitude and season. The modelled volcanic sulphate deposition is compared to the deposition in ice cores following comparable historical eruptions. Furthermore, we evaluate the potential environmental impacts of sulphate deposition. To study inter-model differences, we also compare the CESM2-WACCM6 simulations to similar Icelandic eruption experiments simulated with MAECHAM5-HAM.&#160;

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Methane in the climate system -- from the last glacial to the future

10.5194/egusphere-egu21-12440 ◽

2021 ◽

Author(s):

Thomas Kleinen ◽

Sergey Gromov ◽

Benedikt Steil ◽

Victor Brovkin

Keyword(s):

Radiative Forcing ◽

Ice Cores ◽

Future Climate ◽

Climate System ◽

Max Planck ◽

Atmospheric Concentration ◽

Methane Cycling ◽

Last Glacial ◽

The Future ◽

The Last Glacial

Between the last glacial maximum (LGM) and preindustrial times (PI), the atmospheric concentration of CH4, as shown by reconstructions from ice cores, roughly doubled. It then doubled again from PI to the present. Ice cores, however, cannot tell us how that development will continue in the future, and ice cores also cannot shed light on the causes of the rise in methane, as well as the rapid fluctuations during periods such as the Bolling-Allerod and Younger Dryas.We use a methane-enabled version of MPI-ESM, the Max Planck Institute for Meteorology Earth System Model, to investigate changes in methane cycling in a transient ESM experiment from the LGM to the present, continuing onwards into the future for the next millennium. The model is driven by prescribed orbit, greenhouse gases and ice sheets, with all other changes to the climate system determined internally. Methane cycling is modelled by modules representing the atmospheric transport and sink of methane, as well as terrestrial sources and sinks from soils, termites, and fires. Thus, the full natural methane cycle &#8211; with the exception of geological and animal emissions &#8211; is represented in the model. For historical and future climate, anthropogenic emissions of methane are considered, too.We show that the methane increase since the LGM is largely driven by source changes, with LGM emissions substantially reduced in comparison to the early Holocene and preindustrial states due to lower temperature, CO2, and soil carbon. Depending on the future climate scenario, these dependencies then lead to further increases in CH4, with a further doubling of atmospheric CH4 easily possible if one of the higher radiative forcing scenarios is followed. Furthermore, the future increases in CH4 will persist for a long time, as CH4 only decreases when the climate system cools again.

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Recent Surface Air Temperature Change over Mainland China Based on an Urbanization-Bias Adjusted Dataset

Journal of Climate ◽

10.1175/jcli-d-18-0395.1 ◽

2019 ◽

Vol 32 (10) ◽

pp. 2691-2705 ◽

Cited By ~ 4

Author(s):

Kangmin Wen ◽

Guoyu Ren ◽

Jiao Li ◽

Aiying Zhang ◽

Yuyu Ren ◽

...

Keyword(s):

Air Temperature ◽

North China ◽

Linear Trend ◽

Mainland China ◽

Surface Air Temperature ◽

Data Series ◽

Standard Procedures ◽

Corrected Data ◽

Warming Rate ◽

Temperature Time

Abstract A dataset from 763 national Reference Climate and Basic Meteorological Stations (RCBMS) was used to analyze surface air temperature (SAT) change in mainland China. The monthly historical observational records had been adjusted for urbanization bias existing in the data series of size-varied urban stations, after they were corrected for data inhomogeneities mainly caused by relocation and instrumentation. The standard procedures for creating area-averaged temperature time series and for calculating linear trend were used. Analyses were made for annual and seasonal mean temperature. Annual mean SAT in mainland China as a whole rose by 1.24°C for the last 55 years, with a warming rate of 0.23°C decade−1. This was close to the warming of 1.09°C observed in global mean land SAT over the period 1951–2010. Compared to the SAT before correction, after-corrected data showed that the urbanization bias had caused an overestimate of the annual warming rate of more than 19.6% during 1961–2015. The winter, autumn, spring, and summer mean warming rates were 0.28°, 0.23°, 0.23°, and 0.15°C decade−1, respectively. The spatial patterns of the annual and seasonal mean SAT trends also exhibited an obvious difference from those of the previous analyses. The largest contrast was a weak warming area appearing in central parts of mainland China, which included a small part of southwestern North China, the northwestern Yangtze River, and the eastern part of Southwest China. The annual mean warming trends in Northeast and North China obviously decreased compared to the previous analyses, which caused a relatively more significant cooling in Northeast China after 1998 under the background of global warming slowdown.

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Diagnosing the decline in climatic mass balance of glaciers in Svalbard over 1957–2014

The Cryosphere ◽

10.5194/tc-11-191-2017 ◽

2017 ◽

Vol 11 (1) ◽

pp. 191-215 ◽

Cited By ~ 30

Author(s):

Torbjørn Ims Østby ◽

Thomas Vikhamar Schuler ◽

Jon Ove Hagen ◽

Regine Hock ◽

Jack Kohler ◽

...

Keyword(s):

Mass Balance ◽

Linear Trend ◽

Model Performance ◽

Marked Change ◽

Ice Cores ◽

High Arctic ◽

Reanalysis Data ◽

Svalbard Archipelago ◽

Summer Temperatures

Abstract. Estimating the long-term mass balance of the high-Arctic Svalbard archipelago is difficult due to the incomplete geodetic and direct glaciological measurements, both in space and time. To close these gaps, we use a coupled surface energy balance and snow pack model to analyse the mass changes of all Svalbard glaciers for the period 1957–2014. The model is forced by ERA-40 and ERA-Interim reanalysis data, downscaled to 1 km resolution. The model is validated using snow/firn temperature and density measurements, mass balance from stakes and ice cores, meteorological measurements, snow depths from radar profiles and remotely sensed surface albedo and skin temperatures. Overall model performance is good, but it varies regionally. Over the entire period the model yields a climatic mass balance of 8.2 cm w. e. yr−1, which corresponds to a mass input of 175 Gt. Climatic mass balance has a linear trend of −1.4 ± 0.4 cm w. e. yr−2 with a shift from a positive to a negative regime around 1980. Modelled mass balance exhibits large interannual variability, which is controlled by summer temperatures and further amplified by the albedo feedback. For the recent period 2004–2013 climatic mass balance was −21 cm w. e. yr−1, and accounting for frontal ablation estimated by Błaszczyk et al.(2009) yields a total Svalbard mass balance of −39 cm w. e. yr−1 for this 10-year period. In terms of eustatic sea level, this corresponds to a rise of 0.037 mm yr−1. Refreezing of water in snow and firn is substantial at 22 cm w. e. yr−1 or 26 % of total annual accumulation. However, as warming leads to reduced firn area over the period, refreezing decreases both absolutely and relative to the total accumulation. Negative mass balance and elevated equilibrium line altitudes (ELAs) resulted in massive reduction of the thick (>  2 m) firn extent and an increase in the superimposed ice, thin (<  2 m) firn and bare ice extents. Atmospheric warming also leads to a marked change in the thermal regime, with cooling of the glacier mid-elevation and warming in the ablation zone and upper firn areas. On the long-term, by removing the thermal barrier, this warming has implications for the vertical transfer of surface meltwater through the glacier and down to the base, influencing basal hydrology, sliding and thereby overall glacier motion.

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