ID:39 Description, Causes, and Impacts of Arctic Extremes

22 February 2023 | 16:00 - 18:00 (GMT+1)

Open Session - HYBRID


Room: Hörsaal 2


Session Conveners:  James Overland (NOAA/ Pacific Marine Environmental Laboratory, United States); Timo Vihma (Finnish Meteorological Institute, Finland); Heïdi Sevestre (AMAP, Norway)


Session Description

Arctic extremes are increasing and are often record-shattering (Walsh et al. 2020, Fisher et al. 2021, Overland 2021). Moon et al. (2019) note the expanding footprint of rapid Arctic change. Landrum and Holland (2020) conclude that the Arctic is already transitioning from a cryosphere-dominated system. Taken together (consilience) multiple types of extremes are an indicator of rapid Arctic change relative to trends in single variables such as increasing temperatures.

Natural weather variability interacting with Arctic changes

Twenty years ago, the Arctic was more resilient to climate change than now, as sea ice was broader and three times thicker than today. We examine extreme events, thresholds, tipping points, causes, impacts, and forecasts. Our hypothesis is that new extremes are forced by the interaction of atmosphere, ocean, and other Arctic changes, affecting ecosystems and communities. Fluctuations outside resilience boundaries lead to detrimental impacts.

The term extreme is understood in one of two ways. The first is as a statistical extreme, risk analysis that is defined in terms of rareness. The second is in terms of impacts and leads to a scenario approach. Our goal is to tie together biological/societal impacts of environmental events with extreme weather into joint causal accounts.



  • unfold_moreProjected changes in extreme events over Alaska from regional climate model simulations

    John Walsh
    University of Alaska Fairbanks


    The greatest impacts of climate change are associated with extreme events, and Alaska is a region affected by a variety of extreme events. We have used output from the CORDEX-Arctic simulations to examine the frequency of various threshold exceedances of temperature (high and low), precipitation, wind speed and snowfall. The evaluations are performed on a set of nine regional/global model combinations from CORDEX-Arctic. A quantile-mapping procedure is used to bias-correct the model simulations, and the bias corrections are applied to historical as well as future (RCP 4,5 and RCP 8.5) model output. Extreme cold events show greater changes than extreme warm events over all of Alaska, especially during the winter season, consistent with observational trends. Increases of heavy precipitation events are stronger in the models than in observational data, and changes in heavy snowfall events are strongly dependent on latitude and elevation. Changes in high-wind events vary among models, but higher frequencies of strong winds in western Alaska are projected by a majority of the models.

  • unfold_moreNorth American Extreme Winter Weather and the Polar Vortex

    Muyin Wang1; James Overland2
    1University of Washington; 2NOAA


    Extreme cold weather events during winter in North American can cause huge damages in society’s infrastructure and people’s daily life. A strong link exists between stratospheric variability and anomalous weather patterns at the earth’s surface. Specifically, during extreme variability of the Arctic polar weak vortex event, anomalies can descend from the upper stratosphere to the surface on time scales of weeks. Subsequently the outbreak of cold-air events has been noted in high northern latitudes. In this study we document the recently observed extreme cold events and its connection with Polar Vortex strength and displacement. Because of the importance of stratosphere–troposphere coupling for seasonal climate predictability, identifying the type of stratospheric variability to capture the correct surface response will be necessary.

  • unfold_moreLatitudinal gradients in temperature and precipitation in the ice-free part of Greenland

    Tiago Silva1; Wolfgang Schöner1; Jakob Abermann1
    1University of Graz


    The terrestrial Greenland ecosystem (ice-free area) has been changing strongly, impacting biodiversity. The increased air temperature, and consequently rainfall, alter ecosystem interactions and functioning, with potential endangerment of fragile fauna. Given the complexity of Greenland’s coastal topography and the synoptic scale of atmospheric and oceanic circulation, climatic conditions over ice-free regions are spatially highly heterogeneous. Here, we present air temperature and precipitation evolution over non-glaciated areas as a function of latitude both along Greenland’s East and West coast. Our results are supported by 60+ years output of a state-of-art polar-adapted regional climate model that is validated with meteorological data from observational networks. In addition, we explore changes in the precipitation phase as well as the timing and length of the snow-free period. The prevailing atmospheric circulation pattern plays a major role in shaping the inter-annual air-temperature variability in ice-free regions in both Greenland coasts. This signal is more evident in south Greenland, with certain latitudes recording more frequently annual average temperatures above zero degrees Celsius. The acquired insights will be available for ecosystem consequence analysis where longitudinal variability of climate input is required.

  • unfold_moreHow a summer drought affected land surface energy fluxes in the Siberian tundra

    Nils Rietze1; Gabriela Schaepman-Strub1; Jakob Assmann1; Kathrin Naegeli1; Alexander Damm1
    1University of Zurich


    The rapidly warming climate and associated changes, such as plant community shifts, droughts and wildfires, alter land surface energy fluxes in the Arctic tundra. While intact vegetation can decouple its canopy temperature from ambient air temperature, drought stressed vegetation might lack the ability to cool its canopy by evapotranspiration. The strength of this cooling ability is called thermoregulation and can be detected from the canopy's surface temperature. Our study aims to analyse drivers of plant thermoregulation combining remotely sensed estimates of heat fluxes and in situ data of microclimate. We collected drone-based optical and thermal imagery during peak growth season (July - August) of a very dry summer (2020) and a hydrologically average summer (2021) in the Kytalyk national reserve in north-eastern Siberia. Additionally, we measured biotic, soil and atmospheric variables. We first quantified the drivers of micro-scale thermoregulation across different plant communities, and then investigated the effects of summer drought on thermoregulation. During both years, plant community types differed in their thermoregulation. Communities associated with moist soils had the strongest cooling of the canopy, whereas drier plant communities showed weaker thermoregulation or a complete lack thereof. Thermoregulation was weaker in the summer with drought (2020) across all vegetation types, indicating that the plants experience water limitation during drought conditions at the research site.

  • unfold_moreExtreme precipitation over Svalbard and its relation to the recent decline of sea-ice in the Greenland Sea

    Malte Müller1; Timo Kelder2; Cyril Palerme1
    1Norwegian Meteorological Institute; 2Climate Adaptation Services


    In the last decade, several extreme precipitation events over Svalbard have been observed, which all had a strong impact on the environment and society.
    The most recently observed events in the years 2012, 2016, and 2018, were the highest events in the entire precipitation record from 1974 till today. The key question of our study is, whether those recently observed extremes are part of a climate change signal or are a random accumulation of extremes. Those precipitation extremes are connected to atmospheric rivers, which bring warm and moist air toward higher latitudes. Very few historical observation records exist and thus it is not possible to understand recent changes in the extreme precipitation characteristics over Svalbard from observations only. We developed a novel approach to determine recent trends in extreme weather from a large high-resolution ensemble hindcast. The hindcast is from a seasonal prediction system and is constrained to atmospheric and oceanic reanalysis data. With this large ensemble, the confidence intervals are greatly reduced and it allows us to study instationarity of climate extremes and to identify processes that are drivers for changes in extreme Arctic precipitation. It shows that return values over Svalbard have been changing by about 10 % within the last 35 years and the largest trends are found in the northern parts of Svalbard. The major cause of this change can be attributed to the reduction in sea-ice extent east of Greenland because the presence of sea ice shields the west coast of Svalbard from the incoming southerly moist air. Our analysis suggests, that in the future with a further decline of the sea ice coverage east of Greenland, the recently observed precipitation extremes will become even more frequent.

  • unfold_moreDevelopment of guidance tool to monitor extreme events and rapid biodiversity change in the Arctic

    Susse Wegeberg1; Elmer Topp-Jørgensen1; Floris van Beest1; Kári Fannar Lárusson; Niels Martin Schmidt1; Tom Barry2; Tom Christensen1
    1Aarhus University; 2University of Akureyri


    Extreme weather events are increasing in frequency and intensity across the Arctic, one of the planet’s most rapidly warming regions. Studies from southern latitudes have revealed that the ecological impacts of extreme events on living organisms can be severe and long-lasting. Data and evidence related to extreme events from the terrestrial Arctic biome appear underrepresented, although occurrence of a wide variety of extreme events throughout the Arctic, with multiple and divergent impacts on local biota, are described. Therefore, monitoring short and long-term impacts on biodiversity from extreme weather events in the Arctic is apposite. INTERACT (a network of arctic research stations) and a project, initiated as part of the Circumpolar Biodiversity Monitoring Programme (CBMP, a programme under the Arctic Council working group CAFF, Conservation of Arctic Flora and Fauna), are developing a guidance tool with a monitoring framework for extreme events and their impact on arctic biodiversity and ecosystems. The guidance tool includes suggestions for how to monitor the extreme event itself and the focal ecosystem components (FECs), parameters and attributes that are required to assess both short and long-term biodiversity and ecosystem impacts by linking to existing monitoring plans under the CBMP. The guidance tool includes a number of extreme events relevant for the arctic terrestrial and coastal domains and estimates of their spatio-temporal impacts. The system will eventually be integrated with a set of online toolkits for monitoring arctic biodiversity initiated by CBMP. The guidance tool will be a dynamic framework, and thus be developed, improved and adapted along with expert input and user feedback.