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Prof. Edward Hanna
School of Geography, University of Lincoln, Lincoln, LN6 7FL, UK

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0 Arctic
0 Blocking
0 Climate Change
0 Climatology
0 Glaciology

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Journal article
Published: 09 July 2021 in Sustainability
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Icebergs have long been a threat to shipping in the NW Atlantic and the iceberg season of February to late summer is monitored closely by the International Ice Patrol. However, reliable predictions of the severity of a season several months in advance would be useful for planning monitoring strategies and also for shipping companies in designing optimal routes across the North Atlantic for specific years. A seasonal forecast model of the build-up of seasonal iceberg numbers has recently become available, beginning to enable this longer-term planning of marine operations. Here we discuss extension of this control systems model to include more recent years within the trial ensemble sample set and also increasing the number of measures of the iceberg season that are considered within the forecast. These new measures include the seasonal iceberg total, the rate of change of the seasonal increase, the number of peaks in iceberg numbers experienced within a given season, and the timing of the peak(s). They are predicted by a range of machine learning tools. The skill levels of the new measures are tested, as is the impact of the extensions to the existing seasonal forecast model. We present a forecast for the 2021 iceberg season, predicting a medium iceberg year.

ACS Style

Jennifer Ross; Grant Bigg; Yifan Zhao; Edward Hanna. A Combined Control Systems and Machine Learning Approach to Forecasting Iceberg Flux off Newfoundland. Sustainability 2021, 13, 7705 .

AMA Style

Jennifer Ross, Grant Bigg, Yifan Zhao, Edward Hanna. A Combined Control Systems and Machine Learning Approach to Forecasting Iceberg Flux off Newfoundland. Sustainability. 2021; 13 (14):7705.

Chicago/Turabian Style

Jennifer Ross; Grant Bigg; Yifan Zhao; Edward Hanna. 2021. "A Combined Control Systems and Machine Learning Approach to Forecasting Iceberg Flux off Newfoundland." Sustainability 13, no. 14: 7705.

Article
Published: 13 January 2021 in Climate Dynamics
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We investigate winter Arctic Amplification (AA) on synoptic timescales and at regional scales using a daily version of the Arctic Amplification Index (AAI) and examine causes on a synoptic scale. The persistence, frequency and intensity of high AAI events show significant increases over the Arctic. Similarly, low AAI events are decreasing in frequency, persistence and intensity. In both cases, there are regional variations in these trends, in terms of significance and timing. Significant trends in increasing persistence, frequency and intensity of high AAI events in winter are concentrated in the period 2000–2009, with few significant trends before and after this. There are some decreases in sea-ice concentration in response to synoptic-scale AA events and these AA events can contribute to the decadal trends in AA found in other studies. A sectoral analysis of the Arctic indicates that in the Beaufort–Chukchi and East Siberian–Laptev Seas, synoptic scale high AAI events can be driven by tropical teleconnections while in other Arctic sectors, it is the intrusion of moisture-transporting synoptic cyclones into the Arctic that is most important in synoptic-scale AA. The presence of Rossby wave breaking during high AAI events is indicative of forcing from lower latitudes, modulated by variations in the jet stream. An important conclusion is that the increased persistence, frequency and intensity of synoptic-scale high AAI events make significant contributions to the interannual trend in AA.

ACS Style

Richard J. Hall; Edward Hanna; Linling Chen. Winter Arctic Amplification at the synoptic timescale, 1979–2018, its regional variation and response to tropical and extratropical variability. Climate Dynamics 2021, 56, 457 -473.

AMA Style

Richard J. Hall, Edward Hanna, Linling Chen. Winter Arctic Amplification at the synoptic timescale, 1979–2018, its regional variation and response to tropical and extratropical variability. Climate Dynamics. 2021; 56 (1-2):457-473.

Chicago/Turabian Style

Richard J. Hall; Edward Hanna; Linling Chen. 2021. "Winter Arctic Amplification at the synoptic timescale, 1979–2018, its regional variation and response to tropical and extratropical variability." Climate Dynamics 56, no. 1-2: 457-473.

Research article
Published: 21 December 2020 in International Journal of Climatology
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The Greenland blocking index (GBI), an indicator of the synoptic‐scale circulation over Greenland, has been anomalously positive during most summers since the late 1990s. Such changes in atmospheric circulation, favouring anticyclonic conditions, have led to an increase in Greenland summer temperatures, a decrease in cloud cover and larger surface melt. The GBI is therefore a key indicator of melting and surface mass balance variability over the Greenland ice sheet. However, the models of fifth phase of the Coupled Model Intercomparison Project (CMIP5) do not represent the increase in GBI that is suggested by recent observations, and do not project any significant increase in GBI until 2100. In this study, the new generation of CMIP6 Earth‐system models is evaluated in order to analyse the evolution of the future GBI. All CMIP5 and CMIP6 projections reveal the same trend towards a decrease of the GBI until 2100 and no model reproduces the strong increase in the persistence of summer blocking events observed over the last few decades. Significant melting events related to a highly positive GBI, as observed in summer 2019, are still not considered by CMIP6 models and therefore the projected surface melt increase of the ice sheet could be underestimated if such summer circulation changes persist in the next decades.

ACS Style

Alison Delhasse; Edward Hanna; Christoph Kittel; Xavier Fettweis. Brief communication: CMIP6 does not suggest any atmospheric blocking increase in summer over Greenland by 2100. International Journal of Climatology 2020, 41, 2589 -2596.

AMA Style

Alison Delhasse, Edward Hanna, Christoph Kittel, Xavier Fettweis. Brief communication: CMIP6 does not suggest any atmospheric blocking increase in summer over Greenland by 2100. International Journal of Climatology. 2020; 41 (4):2589-2596.

Chicago/Turabian Style

Alison Delhasse; Edward Hanna; Christoph Kittel; Xavier Fettweis. 2020. "Brief communication: CMIP6 does not suggest any atmospheric blocking increase in summer over Greenland by 2100." International Journal of Climatology 41, no. 4: 2589-2596.

Research article
Published: 13 October 2020 in International Journal of Climatology
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Substantial marine, terrestrial, and atmospheric changes have occurred over the Greenland region during the last century. Several studies have documented record‐levels of Greenland Ice Sheet (GrIS) summer melt extent during the 2000s and 2010s, but relatively little work has been carried out to assess regional climatic changes in other seasons. Here, we focus on the less studied cold‐season (i.e., autumn and winter) climate, tracing the long‐term (1873–2013) variability of Greenland's air temperatures through analyses of coastal observations and model‐derived outlet glacier series and their linkages with North Atlantic sea ice, sea surface temperature (SST), and atmospheric circulation indices. Through a statistical framework, large amounts of west and south Greenland temperature variance (up to r2~50%) can be explained by the seasonally‐contemporaneous combination of the Greenland Blocking Index (GBI) and the North Atlantic Oscillation (NAO; hereafter the combination of GBI and NAO is termed GBI). Lagged and concomitant regional sea‐ice concentration (SIC) and the Atlantic Multidecadal Oscillation (AMO) seasonal indices account for small amounts of residual air temperature variance (r2<~10%) relative to the GBI. The correlations between GBI and cold‐season temperatures are predominantly positive and statistically‐significant through time, while regional SIC conditions emerge as a significant covariate from the mid‐20th century through the conclusion of the study period. The inclusion of the cold‐season Pacific Decadal Oscillation (PDO) in multivariate analyses bolsters the air temperature variance explained by the North Atlantic regional predictors, suggesting the remote, background climate state is important to long‐term Greenland temperature variability. These findings imply that large‐scale tropospheric circulation has a strong control on surface temperature over Greenland through dynamic and thermodynamic impacts and stress the importance of understanding the evolving two‐way linkages between the North Atlantic marine and atmospheric environment in order to more accurately predict Greenland seasonal climate variability and change through the 21st century.

ACS Style

Thomas J. Ballinger; Edward Hanna; Richard J. Hall; J. Rachel Carr; Saber Brasher; Erich C. Osterberg; John Cappelen; Marco Tedesco; Qinghua Ding; Sebastian H. Mernild. The role of blocking circulation and emerging open water feedbacks on Greenland cold‐season air temperature variability over the last century. International Journal of Climatology 2020, 41, 1 .

AMA Style

Thomas J. Ballinger, Edward Hanna, Richard J. Hall, J. Rachel Carr, Saber Brasher, Erich C. Osterberg, John Cappelen, Marco Tedesco, Qinghua Ding, Sebastian H. Mernild. The role of blocking circulation and emerging open water feedbacks on Greenland cold‐season air temperature variability over the last century. International Journal of Climatology. 2020; 41 (S1):1.

Chicago/Turabian Style

Thomas J. Ballinger; Edward Hanna; Richard J. Hall; J. Rachel Carr; Saber Brasher; Erich C. Osterberg; John Cappelen; Marco Tedesco; Qinghua Ding; Sebastian H. Mernild. 2020. "The role of blocking circulation and emerging open water feedbacks on Greenland cold‐season air temperature variability over the last century." International Journal of Climatology 41, no. S1: 1.

Review
Published: 13 September 2020 in Ambio
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Arctic and subarctic ecosystems are experiencing substantial changes in hydrology, vegetation, permafrost conditions, and carbon cycling, in response to climatic change and other anthropogenic drivers, and these changes are likely to continue over this century. The total magnitude of these changes results from multiple interactions among these drivers. Field measurements can address the overall responses to different changing drivers, but are less capable of quantifying the interactions among them. Currently, a comprehensive assessment of the drivers of ecosystem changes, and the magnitude of their direct and indirect impacts on subarctic ecosystems, is missing. The Torneträsk area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years, and is one of the most studied sites in the Arctic. In this study, we summarize and rank the drivers of ecosystem change in the Torneträsk area, and propose research priorities identified, by expert assessment, to improve predictions of ecosystem changes. The research priorities identified include understanding impacts on ecosystems brought on by altered frequency and intensity of winter warming events, evapotranspiration rates, rainfall, duration of snow cover and lake-ice, changed soil moisture, and droughts. This case study can help us understand the ongoing ecosystem changes occurring in the Torneträsk area, and contribute to improve predictions of future ecosystem changes at a larger scale. This understanding will provide the basis for the future mitigation and adaptation plans needed in a changing climate.

ACS Style

Didac Pascual; Jonas Åkerman; Marina Becher; Terry V. Callaghan; Torben R. Christensen; Ellen Dorrepaal; Urban Emanuelsson; Reiner Giesler; Dan Hammarlund; Edward Hanna; Annika Hofgaard; Hongxiao Jin; Cecilia Johansson; Christer Jonasson; Jonatan Klaminder; Jan Karlsson; Erik Lundin; Anders Michelsen; David Olefeldt; Andreas Persson; Gareth K. Phoenix; Zofia Rączkowska; Riikka Rinnan; Lena Ström; Jing Tang; Ruth K. Varner; Philip Wookey; Margareta Johansson. The missing pieces for better future predictions in subarctic ecosystems: A Torneträsk case study. Ambio 2020, 50, 375 -392.

AMA Style

Didac Pascual, Jonas Åkerman, Marina Becher, Terry V. Callaghan, Torben R. Christensen, Ellen Dorrepaal, Urban Emanuelsson, Reiner Giesler, Dan Hammarlund, Edward Hanna, Annika Hofgaard, Hongxiao Jin, Cecilia Johansson, Christer Jonasson, Jonatan Klaminder, Jan Karlsson, Erik Lundin, Anders Michelsen, David Olefeldt, Andreas Persson, Gareth K. Phoenix, Zofia Rączkowska, Riikka Rinnan, Lena Ström, Jing Tang, Ruth K. Varner, Philip Wookey, Margareta Johansson. The missing pieces for better future predictions in subarctic ecosystems: A Torneträsk case study. Ambio. 2020; 50 (2):375-392.

Chicago/Turabian Style

Didac Pascual; Jonas Åkerman; Marina Becher; Terry V. Callaghan; Torben R. Christensen; Ellen Dorrepaal; Urban Emanuelsson; Reiner Giesler; Dan Hammarlund; Edward Hanna; Annika Hofgaard; Hongxiao Jin; Cecilia Johansson; Christer Jonasson; Jonatan Klaminder; Jan Karlsson; Erik Lundin; Anders Michelsen; David Olefeldt; Andreas Persson; Gareth K. Phoenix; Zofia Rączkowska; Riikka Rinnan; Lena Ström; Jing Tang; Ruth K. Varner; Philip Wookey; Margareta Johansson. 2020. "The missing pieces for better future predictions in subarctic ecosystems: A Torneträsk case study." Ambio 50, no. 2: 375-392.

Review
Published: 12 August 2020 in Earth-Science Reviews
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The greatest impacts of climate change on ecosystems, wildlife and humans often arise from extreme events rather than changes in climatic means. Northern high latitudes, including the Arctic, experience a variety of climate-related extreme events, yet there has been little attempt to synthesize information on extreme events in this region. This review surveys work on various types of extreme events in northern high latitudes, addressing (1) the evidence for variations and changes based on analyses of recent historical data and (2) projected changes based primarily on studies utilizing global climate models. The survey of extreme weather and climate events includes temperature, precipitation, snow, freezing rain, atmospheric blocking, cyclones, and wind. The survey also includes cryospheric and biophysical impacts: sea ice rapid loss events, Greenland Ice Sheet melt, floods, drought, wildfire, coastal erosion, terrestrial ecosystems, and marine ecosystems. Temperature and sea ice rank at the high end of the spectra of evidence for change and confidence in future change, while drought, flooding and cyclones rank at the lower end. Research priorities identified on the basis of this review include greater use of high-resolution models and observing system enhancements that target extreme events. There is also a need for further work on attribution, impacts on ecosystems and humans, and thresholds or tipping points that may be triggered by extreme events in high latitudes.

ACS Style

John E. Walsh; Thomas Ballinger; Eugénie S. Euskirchen; Edward Hanna; Johanna Mård; James E. Overland; Helge Tangen; Timo Vihma. Extreme weather and climate events in northern areas: A review. Earth-Science Reviews 2020, 209, 103324 .

AMA Style

John E. Walsh, Thomas Ballinger, Eugénie S. Euskirchen, Edward Hanna, Johanna Mård, James E. Overland, Helge Tangen, Timo Vihma. Extreme weather and climate events in northern areas: A review. Earth-Science Reviews. 2020; 209 ():103324.

Chicago/Turabian Style

John E. Walsh; Thomas Ballinger; Eugénie S. Euskirchen; Edward Hanna; Johanna Mård; James E. Overland; Helge Tangen; Timo Vihma. 2020. "Extreme weather and climate events in northern areas: A review." Earth-Science Reviews 209, no. : 103324.

Research article
Published: 26 July 2020 in International Journal of Climatology
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We provide an updated analysis of instrumental Greenland monthly temperature data to 2019, focusing mainly on coastal stations but also analysing ice‐sheet records from Swiss Camp and Summit. Significant summer (winter) coastal warming of ~1.7 (4.4) °C occurred from 1991‐2019, but since 2001 overall temperature trends are generally flat and insignificant due to a cooling pattern over the last 6‐7 years. Inland and coastal stations show broadly similar temperature trends for summer. Greenland temperature changes are more strongly correlated with Greenland Blocking than with North Atlantic Oscillation changes. In quantifying the association between Greenland coastal temperatures and Greenland Ice Sheet (GrIS) mass‐balance changes, we show a stronger link of temperatures with total mass balance rather than surface mass balance. Based on Greenland coastal temperatures and modelled mass balance for the 1972‐2018 period, each 1°C of summer warming corresponds to ~ (91) 116 Gt yr‐1 of GrIS (surface) mass loss and a 26 Gt yr‐1 increase in solid ice discharge. Given an estimated 4.0‐6.6°C of further Greenland summer warming according to the regional model MAR projections run under CMIP6 future climate projections (SSP5‐8.5 scenario), and assuming that ice‐dynamical losses and ice sheet topography stay similar to the recent past, linear extrapolation gives a corresponding GrIS global sea‐level rise (SLR) contribution of ~10.0‐12.6 cm by 2100, compared with the 8‐27 cm (mean 15 cm) “likely” model projection range reported by IPCC (2019, SPM.B1.2). However, our estimate represents a lower limit for future GrIS change since fixed dynamical mass losses and amplified melt arising from both melt‐albedo and melt‐elevation positive feedbacks are not taken into account here. This article is protected by copyright. All rights reserved.

ACS Style

Edward Hanna; John Cappelen; Xavier Fettweis; Sebastian H. Mernild; Thomas L. Mote; Ruth Mottram; Konrad Steffen; Thomas J. Ballinger; Richard J. Hall. Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change. International Journal of Climatology 2020, 41, 1 .

AMA Style

Edward Hanna, John Cappelen, Xavier Fettweis, Sebastian H. Mernild, Thomas L. Mote, Ruth Mottram, Konrad Steffen, Thomas J. Ballinger, Richard J. Hall. Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change. International Journal of Climatology. 2020; 41 (S1):1.

Chicago/Turabian Style

Edward Hanna; John Cappelen; Xavier Fettweis; Sebastian H. Mernild; Thomas L. Mote; Ruth Mottram; Konrad Steffen; Thomas J. Ballinger; Richard J. Hall. 2020. "Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change." International Journal of Climatology 41, no. S1: 1.

Journal article
Published: 22 June 2020 in Atmosphere
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Public attention has recently focused on high-impact extreme weather events in midlatitudes that originate in the sub-Arctic. We investigate movements of the stratospheric polar vortex (SPV) and related changes in lower atmospheric circulation during the February-March 2018 “Beast from the East” cold winter event that dramatically affected much of Europe and north-central North America. This study demonstrates that the movement of the SPV is a key linkage in late winter subarctic and northern midlatitude extreme weather events. February–March 2018 saw two types of subarctic-midlatitude weather connections. In the first type, the SPV was displaced from the pole to lower latitudes over North America in February and then was found over northern Siberia in March. Mid-February and mid-March are examples of persistent near vertically aligned geopotential height structures of the atmospheric circulation. These structures over North America and Eurasia advected cold Arctic air southward. The second type of cold surface event was associated with a weak regional SPV and a sudden stratospheric warming event over Europe during the second half of February. These late winter linkage events that arise through dynamic instabilities of the SPV are more common in the last decade, but the potential role of enhanced Arctic amplification is uncertain.

ACS Style

James Overland; Richard Hall; Edward Hanna; Alexey Karpechko; Timo Vihma; Muyin Wang; Xiangdong Zhang. The Polar Vortex and Extreme Weather: The Beast from the East in Winter 2018. Atmosphere 2020, 11, 664 .

AMA Style

James Overland, Richard Hall, Edward Hanna, Alexey Karpechko, Timo Vihma, Muyin Wang, Xiangdong Zhang. The Polar Vortex and Extreme Weather: The Beast from the East in Winter 2018. Atmosphere. 2020; 11 (6):664.

Chicago/Turabian Style

James Overland; Richard Hall; Edward Hanna; Alexey Karpechko; Timo Vihma; Muyin Wang; Xiangdong Zhang. 2020. "The Polar Vortex and Extreme Weather: The Beast from the East in Winter 2018." Atmosphere 11, no. 6: 664.

Research article
Published: 29 January 2020 in The Cryosphere
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Melting of the Greenland Ice Sheet (GrIS) is the largest single contributor to eustatic sea level and is amplified by the growth of pigmented algae on the ice surface, which increases solar radiation absorption. This biological albedo-reducing effect and its impact upon sea level rise has not previously been quantified. Here, we combine field spectroscopy with a radiative-transfer model, supervised classification of unmanned aerial vehicle (UAV) and satellite remote-sensing data, and runoff modelling to calculate biologically driven ice surface ablation. We demonstrate that algal growth led to an additional 4.4–6.0 Gt of runoff from bare ice in the south-western sector of the GrIS in summer 2017, representing 10 %–13 % of the total. In localized patches with high biomass accumulation, algae accelerated melting by up to 26.15±3.77 % (standard error, SE). The year 2017 was a high-albedo year, so we also extended our analysis to the particularly low-albedo 2016 melt season. The runoff from the south-western bare-ice zone attributed to algae was much higher in 2016 at 8.8–12.2 Gt, although the proportion of the total runoff contributed by algae was similar at 9 %–13 %. Across a 10 000 km2 area around our field site, algae covered similar proportions of the exposed bare ice zone in both years (57.99 % in 2016 and 58.89 % in 2017), but more of the algal ice was classed as “high biomass” in 2016 (8.35 %) than 2017 (2.54 %). This interannual comparison demonstrates a positive feedback where more widespread, higher-biomass algal blooms are expected to form in high-melt years where the winter snowpack retreats further and earlier, providing a larger area for bloom development and also enhancing the provision of nutrients and liquid water liberated from melting ice. Our analysis confirms the importance of this biological albedo feedback and that its omission from predictive models leads to the systematic underestimation of Greenland's future sea level contribution, especially because both the bare-ice zones available for algal colonization and the length of the biological growth season are set to expand in the future.

ACS Style

Joseph M. Cook; Andrew J. Tedstone; Christopher Williamson; Jenine McCutcheon; Andrew J. Hodson; Archana Dayal; McKenzie Skiles; Stefan Hofer; Robert Bryant; Owen McAree; Andrew McGonigle; Jonathan Ryan; Alexandre M. Anesio; Tristram D. L. Irvine-Fynn; Alun Hubbard; Edward Hanna; Mark Flanner; Sathish Mayanna; Liane G. Benning; Dirk van As; Marian Yallop; James B. McQuaid; Thomas Gribbin; Martyn Tranter. Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet. The Cryosphere 2020, 14, 309 -330.

AMA Style

Joseph M. Cook, Andrew J. Tedstone, Christopher Williamson, Jenine McCutcheon, Andrew J. Hodson, Archana Dayal, McKenzie Skiles, Stefan Hofer, Robert Bryant, Owen McAree, Andrew McGonigle, Jonathan Ryan, Alexandre M. Anesio, Tristram D. L. Irvine-Fynn, Alun Hubbard, Edward Hanna, Mark Flanner, Sathish Mayanna, Liane G. Benning, Dirk van As, Marian Yallop, James B. McQuaid, Thomas Gribbin, Martyn Tranter. Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet. The Cryosphere. 2020; 14 (1):309-330.

Chicago/Turabian Style

Joseph M. Cook; Andrew J. Tedstone; Christopher Williamson; Jenine McCutcheon; Andrew J. Hodson; Archana Dayal; McKenzie Skiles; Stefan Hofer; Robert Bryant; Owen McAree; Andrew McGonigle; Jonathan Ryan; Alexandre M. Anesio; Tristram D. L. Irvine-Fynn; Alun Hubbard; Edward Hanna; Mark Flanner; Sathish Mayanna; Liane G. Benning; Dirk van As; Marian Yallop; James B. McQuaid; Thomas Gribbin; Martyn Tranter. 2020. "Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet." The Cryosphere 14, no. 1: 309-330.

Review article
Published: 23 November 2019 in Earth-Science Reviews
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Recent research shows increasing decadal ice mass losses from the Greenland and Antarctic Ice Sheets and more generally from glaciers worldwide in the light of continued global warming. Here, in an update of our previous ISMASS paper (Hanna et al., 2013), we review recent observational estimates of ice sheet and glacier mass balance, and their related uncertainties, first briefly considering relevant monitoring methods. Focusing on the response to climate change during 1992-2018, and especially the post-IPCC AR5 period, we discuss recent changes in the relative contributions of ice sheets and glaciers to sea-level change. We assess recent advances in understanding of the relative importance of surface mass balance and ice dynamics in overall ice-sheet mass change. We also consider recent improvements in ice-sheet modelling, highlighting data-model linkages and the use of updated observational datasets in ice-sheet models. Finally, by identifying key deficiencies in the observations and models that hamper current understanding and limit reliability of future ice-sheet projections, we make recommendations to the research community for reducing these knowledge gaps. Our synthesis aims to provide a critical and timely review of the current state of the science in advance of the next Intergovernmental Panel on Climate Change Assessment Report that is due in 2021.

ACS Style

Edward Hanna; Frank Pattyn; Francisco Navarro; Vincent Favier; Heiko Goelzer; Michiel R. Van Den Broeke; Miren Vizcaino; Pippa L. Whitehouse; Catherine Ritz; Kevin Bulthuis; Ben Smith. Mass balance of the ice sheets and glaciers – Progress since AR5 and challenges. Earth-Science Reviews 2019, 201, 102976 .

AMA Style

Edward Hanna, Frank Pattyn, Francisco Navarro, Vincent Favier, Heiko Goelzer, Michiel R. Van Den Broeke, Miren Vizcaino, Pippa L. Whitehouse, Catherine Ritz, Kevin Bulthuis, Ben Smith. Mass balance of the ice sheets and glaciers – Progress since AR5 and challenges. Earth-Science Reviews. 2019; 201 ():102976.

Chicago/Turabian Style

Edward Hanna; Frank Pattyn; Francisco Navarro; Vincent Favier; Heiko Goelzer; Michiel R. Van Den Broeke; Miren Vizcaino; Pippa L. Whitehouse; Catherine Ritz; Kevin Bulthuis; Ben Smith. 2019. "Mass balance of the ice sheets and glaciers – Progress since AR5 and challenges." Earth-Science Reviews 201, no. : 102976.

Journal article
Published: 30 August 2019 in The Cryosphere
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One consequence of recent Arctic warming is an increased occurrence and longer seasonality of above-freezing air temperature episodes. There is significant disagreement in the literature concerning potential physical connectivity between high-latitude open water duration proximate to the Greenland Ice Sheet (GrIS) and late-season (i.e., end-of-summer and autumn) GrIS melt events. Here, a new date of sea ice advance (DOA) product is used to determine the occurrence of Baffin Bay sea ice growth along Greenland's west coast for the 2011–2015 period. Over the 2-month period preceding the DOA, northwest Atlantic Ocean and atmospheric conditions are analyzed and linked to late-season melt events observed at a series of on-ice automatic weather stations (AWSs) along the K-transect in southwestern Greenland. Surrounding ice sheet, tundra, and coastal winds from the Modèle Atmosphérique Régional (MAR) and Regional Atmospheric Climate Model (RACMO) provide high-resolution spatial context to AWS observations and are analyzed along with ERA-Interim reanalysis fields to understand the meso-to-synoptic-scale (thermo)dynamic drivers of the melt events. Results suggest that late-season melt events, which primarily occur in the ablation area, are strongly affected by ridging atmospheric circulation patterns that transport warm, moist air from the subpolar North Atlantic toward west Greenland. Increasing concentrations of North Atlantic water vapor are shown to be necessary to produce melt conditions as autumn progresses. While thermal conduction and advection off south Baffin Bay open waters impact coastal air temperatures, local marine air incursions are obstructed by barrier flows and persistent katabatic winds along the western GrIS margin.

ACS Style

Thomas J. Ballinger; Thomas L. Mote; Kyle Mattingly; Angela C. Bliss; Edward Hanna; Dirk Van As; Melissa Prieto; Saeideh Gharehchahi; Xavier Fettweis; Brice Noël; Paul C. J. P. Smeets; Carleen H. Reijmer; Mads H. Ribergaard; John Cappelen. Greenland Ice Sheet late-season melt: investigating multiscale drivers of K-transect events. The Cryosphere 2019, 13, 2241 -2257.

AMA Style

Thomas J. Ballinger, Thomas L. Mote, Kyle Mattingly, Angela C. Bliss, Edward Hanna, Dirk Van As, Melissa Prieto, Saeideh Gharehchahi, Xavier Fettweis, Brice Noël, Paul C. J. P. Smeets, Carleen H. Reijmer, Mads H. Ribergaard, John Cappelen. Greenland Ice Sheet late-season melt: investigating multiscale drivers of K-transect events. The Cryosphere. 2019; 13 (8):2241-2257.

Chicago/Turabian Style

Thomas J. Ballinger; Thomas L. Mote; Kyle Mattingly; Angela C. Bliss; Edward Hanna; Dirk Van As; Melissa Prieto; Saeideh Gharehchahi; Xavier Fettweis; Brice Noël; Paul C. J. P. Smeets; Carleen H. Reijmer; Mads H. Ribergaard; John Cappelen. 2019. "Greenland Ice Sheet late-season melt: investigating multiscale drivers of K-transect events." The Cryosphere 13, no. 8: 2241-2257.

Research article
Published: 08 July 2019 in International Journal of Climatology
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We investigate factors influencing European winter (DJFM) air temperatures for the period 1979–2015 with the focus on changes during the recent period of rapid Arctic warming (1998–2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and back‐trajectory airmass identification. In all five selected European regions, severe cold winter events lasting at least 4 days are significantly correlated with warm Arctic episodes. Relationships during opposite conditions of warm Europe/cold Arctic are also significant. Correlations have become consistently stronger since 1998. Large‐scale pattern analysis reveals that cold spells are associated with the negative phase of the North Atlantic Oscillation (NAO‐) and the positive phase of the Scandinavian (SCA+) pattern, which in turn are correlated with the divergence of dry‐static energy transport. Warm European extremes are associated with opposite phases of these patterns and the convergence of latent heat transport. Airmass trajectory analysis is consistent with these findings, as airmasses associated with extreme cold events typically originate over continents, while warm events tend to occur with prevailing maritime airmasses. Despite Arctic‐wide warming, significant cooling has occurred in northeastern Europe owing to a decrease in adiabatic subsidence heating in airmasses arriving from the southeast, along with increased occurrence of circulation patterns favouring low temperature advection. These dynamic effects dominated over the increased mean temperature of most circulation patterns. Lagged correlation analysis reveals that SCA‐ and NAO+ are typically preceded by cold Arctic anomalies during the previous 2–3 months, which may aid seasonal forecasting.

ACS Style

Timo Vihma; Rune Graversen; Linling Chen; Dörthe Handorf; Natasa Skific; Jennifer A. Francis; Nicholas Tyrrell; Richard Hall; Edward Hanna; Petteri Uotila; Klaus Dethloff; Alexey Y. Karpechko; Halldor Björnsson; James E. Overland. Effects of the tropospheric large‐scale circulation on European winter temperatures during the period of amplified Arctic warming. International Journal of Climatology 2019, 40, 509 -529.

AMA Style

Timo Vihma, Rune Graversen, Linling Chen, Dörthe Handorf, Natasa Skific, Jennifer A. Francis, Nicholas Tyrrell, Richard Hall, Edward Hanna, Petteri Uotila, Klaus Dethloff, Alexey Y. Karpechko, Halldor Björnsson, James E. Overland. Effects of the tropospheric large‐scale circulation on European winter temperatures during the period of amplified Arctic warming. International Journal of Climatology. 2019; 40 (1):509-529.

Chicago/Turabian Style

Timo Vihma; Rune Graversen; Linling Chen; Dörthe Handorf; Natasa Skific; Jennifer A. Francis; Nicholas Tyrrell; Richard Hall; Edward Hanna; Petteri Uotila; Klaus Dethloff; Alexey Y. Karpechko; Halldor Björnsson; James E. Overland. 2019. "Effects of the tropospheric large‐scale circulation on European winter temperatures during the period of amplified Arctic warming." International Journal of Climatology 40, no. 1: 509-529.

Original research article
Published: 03 July 2019 in Frontiers in Microbiology
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Current research into bacterial dynamics on the Greenland Ice Sheet (GrIS) is biased toward cryoconite holes, despite this habitat covering less than 8% of the ablation (melt) zone surface. In contrast, the expansive surface ice, which supports wide-spread Streptophyte micro-algal blooms thought to enhance surface melt, has been relatively neglected. This study aims to understand variability in bacterial abundance and production across an ablation season on the GrIS, in relation to micro-algal bloom dynamics. Bacterial abundance reached 3.3 ± 0.3 × 105 cells ml−1 in surface ice and was significantly linearly related to algal abundances during the middle and late ablation periods (R2 = 0.62, p < 0.05; R2 = 0.78, p < 0.001). Bacterial production (BP) of 0.03–0.6 μg C L−1 h−1 was observed in surface ice and increased in concert with glacier algal abundances, indicating that heterotrophic bacteria consume algal-derived dissolved organic carbon. However, BP remained at least 28 times lower than net primary production, indicating inefficient carbon cycling by heterotrophic bacteria and net accumulation of carbon in surface ice throughout the ablation season. Across the supraglacial environment, cryoconite sediment BP was at least four times greater than surface ice, confirming that cryoconite holes are the true “hot spots” of heterotrophic bacterial activity.

ACS Style

Miranda Jane Nicholes; Christopher James Williamson; Martyn Tranter; Alexandra Holland; Ewa Poniecka; Marian Louise Yallop; Alexandre Anesio; The Black & Bloom Group; Liane Benning; Jim McQuaid; Stefanie Lutz; Jenine McCutcheon; Andy Hodson; Edward Hanna; Tristam Irvine-Fynn; Joseph Cook; Jonathan Bamber; Andrew Tedstone; Jason Box; Marek Stibal. Bacterial Dynamics in Supraglacial Habitats of the Greenland Ice Sheet. Frontiers in Microbiology 2019, 10, 1366 .

AMA Style

Miranda Jane Nicholes, Christopher James Williamson, Martyn Tranter, Alexandra Holland, Ewa Poniecka, Marian Louise Yallop, Alexandre Anesio, The Black & Bloom Group, Liane Benning, Jim McQuaid, Stefanie Lutz, Jenine McCutcheon, Andy Hodson, Edward Hanna, Tristam Irvine-Fynn, Joseph Cook, Jonathan Bamber, Andrew Tedstone, Jason Box, Marek Stibal. Bacterial Dynamics in Supraglacial Habitats of the Greenland Ice Sheet. Frontiers in Microbiology. 2019; 10 ():1366.

Chicago/Turabian Style

Miranda Jane Nicholes; Christopher James Williamson; Martyn Tranter; Alexandra Holland; Ewa Poniecka; Marian Louise Yallop; Alexandre Anesio; The Black & Bloom Group; Liane Benning; Jim McQuaid; Stefanie Lutz; Jenine McCutcheon; Andy Hodson; Edward Hanna; Tristam Irvine-Fynn; Joseph Cook; Jonathan Bamber; Andrew Tedstone; Jason Box; Marek Stibal. 2019. "Bacterial Dynamics in Supraglacial Habitats of the Greenland Ice Sheet." Frontiers in Microbiology 10, no. : 1366.

Articles
Published: 20 June 2019 in Journal of Operational Oceanography
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The iceberg hazard for the Grand Banks area to the east of Newfoundland varies dramatically from one year to the next. In some years no icebergs penetrate south of 48°N, while in others well over 1000 icebergs enter the main shipping lanes between Europe and NE North America. Advance knowledge of this seasonal hazard would have major implications for ship routing, as well as the resources required for maintaining an effective ice hazard service. Here, a Windowed Error Reduction Ratio control system identification approach is used to forecast the severity of the 2018 iceberg season off Newfoundland, in terms of the predicted number of icebergs crossing 48°N, as well as to hindcast iceberg numbers for 2017. The best estimates are for 766 ± 297 icebergs crossing 48°N before the end of September 2017 and 685 ± 207 for 2018. These are both above the recent observed average of 592 icebergs for that date, and substantially so for 2017. Given the bimodal nature of the annual iceberg number, this means that our predictions for both 2017 and 2018 are for a high iceberg season, with a 71% level of confidence. However, it is most likely that the 2018 iceberg numbers will be somewhat less than 1000, while our higher hindcast for 2017 is consistent with the observed level of 1008. Our verification analysis, covering the 20-year period up to 2016, shows our model's correspondence to the high or low nature of the 48°N iceberg numbers is statistically robust to the 0.05% level, with a skill level of 80%.

ACS Style

Grant R. Bigg; Yifan Zhao; Edward Hanna. Forecasting the severity of the Newfoundland iceberg season using a control systems model. Journal of Operational Oceanography 2019, 14, 24 -36.

AMA Style

Grant R. Bigg, Yifan Zhao, Edward Hanna. Forecasting the severity of the Newfoundland iceberg season using a control systems model. Journal of Operational Oceanography. 2019; 14 (1):24-36.

Chicago/Turabian Style

Grant R. Bigg; Yifan Zhao; Edward Hanna. 2019. "Forecasting the severity of the Newfoundland iceberg season using a control systems model." Journal of Operational Oceanography 14, no. 1: 24-36.

Research article
Published: 01 June 2019 in Quarterly Journal of the Royal Meteorological Society
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Seasonal forecasts of winter North Atlantic atmospheric variability have until recently shown little skill. Here we present a new technique for developing both linear and non‐linear statistical forecasts of the winter North Atlantic Oscillation (NAO) based on complex systems modelling, which has been widely used in a range of fields, but generally not in climate research. Our polynomial NARMAX models demonstrate considerable skill in out‐of‐sample forecasts and their performance is superior to that of linear models, albeit with small sample sizes. Predictors can be readily identified and this has the potential to inform the next generation of dynamical models and models allow for the incorporation of non‐linearities in interactions between predictors and atmospheric variability. In general there is more skill in forecasts developed over a shorter training period from 1980 compared with an equivalent forecast using training data from 1956. This latter point may relate to decreased inherent predictability in the period 1955‐1980, a wider range of available predictors since 1980 and/or reduced data quality in the earlier period and is consistent with previously identified decadal variability of the NAO. A number of predictors such as sea‐level pressure over the Barents Sea, and a clear tropical signal are commonly selected by both linear and polynomial NARMAX models. Tropical signals are modulated by higher latitude boundary conditions. Both approaches can be extended to developing probabilistic forecasts and to other seasons and indices of atmospheric variability such as the East Atlantic pattern and jet stream metrics. This article is protected by copyright. All rights reserved.

ACS Style

Richard J. Hall; Hua‐Liang Wei; Edward Hanna. Complex systems modelling for statistical forecasting of winter North Atlantic atmospheric variability: A new approach to North Atlantic seasonal forecasting. Quarterly Journal of the Royal Meteorological Society 2019, 145, 2568 -2585.

AMA Style

Richard J. Hall, Hua‐Liang Wei, Edward Hanna. Complex systems modelling for statistical forecasting of winter North Atlantic atmospheric variability: A new approach to North Atlantic seasonal forecasting. Quarterly Journal of the Royal Meteorological Society. 2019; 145 (723):2568-2585.

Chicago/Turabian Style

Richard J. Hall; Hua‐Liang Wei; Edward Hanna. 2019. "Complex systems modelling for statistical forecasting of winter North Atlantic atmospheric variability: A new approach to North Atlantic seasonal forecasting." Quarterly Journal of the Royal Meteorological Society 145, no. 723: 2568-2585.

Preprint content
Published: 08 December 2018
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A number of insitu and passive microwave satellite sensors have observed Arctic sea ice and Greenland Ice Sheet (GrIS) mass loss trends over recent decades. Along with sea and land ice declines, above-freezing, near-surface air temperatures are observed earlier in boreal spring and later in autumn thus extending periods of melt beyond the core of summer (JJA). Little is known about whether lengthening periods of open ocean proximate to the ice sheet, for instance, demonstrably effect unseasonal GrIS melt events. Here, a new Baffin Bay sea ice advance dataset is utilized to determine dates of sea ice growth along Greenland’s west coast for the 2011-2015 period. Preceding, multi-scale ocean-atmospheric conditions, including at the Baffin-GrIS interface, are analyzed and linked to unseasonal melt events observed at a series of on-ice automatic weather stations (AWS) along the K-transect in southwest Greenland. The local marine versus synoptic influence on the above and below freezing surface air temperature events is assessed through analyses involving AWS winds, pressure, and humidity observations. These surface observations are further compared against Modele Atmospherique Regional (MAR), Regional Atmospheric Climate Model (RACMO), and ERA-Interim reanalysis fields to understand the airmass origins and (thermo)dynamic drivers of the melt events. Results suggest that the K-transect transition season melt events, primarily in the ablation zone, are strongly affected by ridging atmospheric circulation patterns that transport warm, moist air from lower latitude land-ocean areas toward west Greenland. While local conduction of oceanic surface heat appears to impact coastal air temperatures, consistent with previous studies, marine air incursions from Baffin waters onto the ice sheet are likely obstructed by barrier flows and the pressure gradient-driven katabatic regime off of central Greenland.

ACS Style

Thomas Ballinger; Thomas Mote; Kyle Mattingly; Edward Hanna; Angela Bliss; Dirk Van As; Melissa Prieto; Saeideh Gharehchahi; Xavier Fettweis; Brice Noël; Paul Smeets; Mads Ribergaard. Are transition season melt events on the Greenland Ice Sheet driven by Baffin Bay sea ice-atmosphere interactions? 2018, 1 .

AMA Style

Thomas Ballinger, Thomas Mote, Kyle Mattingly, Edward Hanna, Angela Bliss, Dirk Van As, Melissa Prieto, Saeideh Gharehchahi, Xavier Fettweis, Brice Noël, Paul Smeets, Mads Ribergaard. Are transition season melt events on the Greenland Ice Sheet driven by Baffin Bay sea ice-atmosphere interactions? . 2018; ():1.

Chicago/Turabian Style

Thomas Ballinger; Thomas Mote; Kyle Mattingly; Edward Hanna; Angela Bliss; Dirk Van As; Melissa Prieto; Saeideh Gharehchahi; Xavier Fettweis; Brice Noël; Paul Smeets; Mads Ribergaard. 2018. "Are transition season melt events on the Greenland Ice Sheet driven by Baffin Bay sea ice-atmosphere interactions?" , no. : 1.

Review article
Published: 12 November 2018 in Nature Climate Change
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Even if anthropogenic warming were constrained to less than 2 °C above pre-industrial, the Greenland and Antarctic ice sheets will continue to lose mass this century, with rates similar to those observed over the past decade. However, nonlinear responses cannot be excluded, which may lead to larger rates of mass loss. Furthermore, large uncertainties in future projections still remain, pertaining to knowledge gaps in atmospheric (Greenland) and oceanic (Antarctica) forcing. On millennial timescales, both ice sheets have tipping points at or slightly above the 1.5–2.0 °C threshold; for Greenland, this may lead to irreversible mass loss due to the surface mass balance–elevation feedback, whereas for Antarctica, this could result in a collapse of major drainage basins due to ice-shelf weakening.

ACS Style

Frank Pattyn; Catherine Ritz; Edward Hanna; Xylar Asay-Davis; Rob DeConto; Gaël Durand; Lionel Favier; Xavier Fettweis; Heiko Goelzer; Nicholas R. Golledge; Peter Kuipers Munneke; Jan T. M. Lenaerts; Sophie Nowicki; Antony J. Payne; Alexander Robinson; Hélène Seroussi; Luke D. Trusel; Michiel Van Den Broeke. The Greenland and Antarctic ice sheets under 1.5 °C global warming. Nature Climate Change 2018, 8, 1053 -1061.

AMA Style

Frank Pattyn, Catherine Ritz, Edward Hanna, Xylar Asay-Davis, Rob DeConto, Gaël Durand, Lionel Favier, Xavier Fettweis, Heiko Goelzer, Nicholas R. Golledge, Peter Kuipers Munneke, Jan T. M. Lenaerts, Sophie Nowicki, Antony J. Payne, Alexander Robinson, Hélène Seroussi, Luke D. Trusel, Michiel Van Den Broeke. The Greenland and Antarctic ice sheets under 1.5 °C global warming. Nature Climate Change. 2018; 8 (12):1053-1061.

Chicago/Turabian Style

Frank Pattyn; Catherine Ritz; Edward Hanna; Xylar Asay-Davis; Rob DeConto; Gaël Durand; Lionel Favier; Xavier Fettweis; Heiko Goelzer; Nicholas R. Golledge; Peter Kuipers Munneke; Jan T. M. Lenaerts; Sophie Nowicki; Antony J. Payne; Alexander Robinson; Hélène Seroussi; Luke D. Trusel; Michiel Van Den Broeke. 2018. "The Greenland and Antarctic ice sheets under 1.5 °C global warming." Nature Climate Change 8, no. 12: 1053-1061.

Brief communication
Published: 16 October 2018 in The Cryosphere
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Recent studies note a significant increase in high-pressure blocking over the Greenland region (Greenland Blocking Index, GBI) in summer since the 1990s. Such a general circulation change, indicated by a negative trend in the North Atlantic Oscillation (NAO) index, is generally highlighted as a major driver of recent surface melt records observed on the Greenland Ice Sheet (GrIS). Here we compare reanalysis-based GBI records with those from the Coupled Model Intercomparison Project 5 (CMIP5) suite of global climate models over 1950–2100. We find that the recent summer GBI increase lies well outside the range of modelled past reconstructions and future GBI projections (RCP4.5 and RCP8.5). The models consistently project a future decrease in GBI (linked to an increase in NAO), which highlights a likely key deficiency of current climate models if the recently observed circulation changes continue to persist. Given well-established connections between atmospheric pressure over the Greenland region and air temperature and precipitation extremes downstream, e.g. over northwest Europe, this brings into question the accuracy of simulated North Atlantic jet stream changes and resulting climatological anomalies over densely populated regions of northern Europe as well as of future projections of GrIS mass balance produced using global and regional climate models.

ACS Style

Edward Hanna; Xavier Fettweis; Richard J. Hall. Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models. The Cryosphere 2018, 12, 3287 -3292.

AMA Style

Edward Hanna, Xavier Fettweis, Richard J. Hall. Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models. The Cryosphere. 2018; 12 (10):3287-3292.

Chicago/Turabian Style

Edward Hanna; Xavier Fettweis; Richard J. Hall. 2018. "Brief communication: Recent changes in summer Greenland blocking captured by none of the CMIP5 models." The Cryosphere 12, no. 10: 3287-3292.

Research article
Published: 17 August 2018 in International Journal of Climatology
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The “Warm‐Arctic/Cold‐continents” (WACC) winter weather pattern is investigated using the European Centre for Medium‐Range Weather Forecasts 20th Century reanalysis data (ERA20C) spanning 1901–2010. Both the 1920–1940 and 1990–2010 periods are characterized by Arctic amplification (AA) and mid‐latitude continental cooling, although the Arctic warming signal for 1990–2010 is twice as strong as that for 1920–1940. Significant weakening in the mid‐latitude polewards temperature gradient and zonal wind, wavier upper‐level flow character, and strong regional blocking frequency/intensity changes are also detected during both AA periods. These results based on statistical analyses highlight the possible role of AA in affecting mid‐latitude weather patterns, but further work is needed to quantify the influence of AA on particular mid‐latitude dynamical features.

ACS Style

Linling Chen; Jennifer Francis; Edward Hanna. The “Warm-Arctic/Cold-continents” pattern during 1901-2010. International Journal of Climatology 2018, 38, 5245 -5254.

AMA Style

Linling Chen, Jennifer Francis, Edward Hanna. The “Warm-Arctic/Cold-continents” pattern during 1901-2010. International Journal of Climatology. 2018; 38 (14):5245-5254.

Chicago/Turabian Style

Linling Chen; Jennifer Francis; Edward Hanna. 2018. "The “Warm-Arctic/Cold-continents” pattern during 1901-2010." International Journal of Climatology 38, no. 14: 5245-5254.

Research article
Published: 13 July 2018 in International Journal of Climatology
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One of the defining features of both recent and historical cases of global climate change is Arctic amplification (AA). This is the more rapid change in the surface air temperature (SAT) in the Arctic compared to some wider reference region, such as the Northern Hemisphere (NH) mean. Many different metrics have been developed to quantify the degree of AA based on SAT anomalies, trends and variability. The use of different metrics, as well as the choice of data set to use, can affect conclusions about the magnitude and temporal variability of AA. Here we review the established metrics of AA to see how well they agree upon the temporal signature of AA, such as the multi‐decadal variability, and assess the consistency in these metrics across different commonly used data sets which cover both the early and late 20th century warming in the Arctic. We find the NOAA 20th century reanalysis most closely matches the observations when using metrics based upon SAT trends (A2), variability (A3) and regression (A4) of the SAT anomalies, and the ERA 20th century reanalysis is closest to the observations in the SAT anomalies (A1) and variability of SAT anomalies (A3). However, there are large seasonal differences in the consistency between data sets. Moreover, the largest differences between the century‐long reanalysis products and observations are during the early warming period, likely due to the sparseness of the observations in the Arctic at that time. In the modern warming period, the high density of observations strongly constrains all the reanalysis products, whether they include satellite observations or only surface observations. Thus, all the reanalysis and observation products produce very similar magnitudes and temporal variability in the degree of AA during the recent warming period.

ACS Style

Richard Davy; Linling Chen; Edward Hanna. Arctic amplification metrics. International Journal of Climatology 2018, 38, 4384 -4394.

AMA Style

Richard Davy, Linling Chen, Edward Hanna. Arctic amplification metrics. International Journal of Climatology. 2018; 38 (12):4384-4394.

Chicago/Turabian Style

Richard Davy; Linling Chen; Edward Hanna. 2018. "Arctic amplification metrics." International Journal of Climatology 38, no. 12: 4384-4394.