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  1. Conference proceedings ; Online: Tales from the disappearing Arctic ice

    Notz, D.

    XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

    2023  

    Abstract: What can we learn from the waning Arctic sea ice? About the Arctic climate system, our impacts on it, about the Earth system as a whole? This presentation explores these questions from a variety of angles, bringing together models and observations, the ... ...

    Abstract What can we learn from the waning Arctic sea ice? About the Arctic climate system, our impacts on it, about the Earth system as a whole? This presentation explores these questions from a variety of angles, bringing together models and observations, the millimetre scale of sea-ice crystals and large scale global impacts, climate-model projections of future Arctic sea ice and our own inability to preserve the Arctic summer sea-ice cover. The ongoing loss of Arctic sea ice is among the most pronounced consequences of global warming that we have observed so far. Because of the very high signal-to-noise ratio of the satellite record over the past 40 years, the observed sea-ice retreat can be interpreted as a highly sensitive proxy for our ability to understand the climate system, to model its change, to assess its future evolution, and to draw the necessary consequences from these insights. This is the more the case as many of the governing processes are surprisingly linear, which in principle allows one to greatly simplify the complexity of the presented analyses for example of Arctic amplification, climate sensitivity, Arctic clouds, and the response of radiative fluxes.
    Subject code 550
    Language English
    Publishing country de
    Document type Conference proceedings ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: How well must climate models agree with observations?

    Notz, Dirk

    Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

    2015  Volume 373, Issue 2052

    Abstract: The usefulness of a climate-model simulation cannot be inferred solely from its degree of agreement with observations. Instead, one has to consider additional factors such as internal variability, the tuning of the model, observational uncertainty, the ... ...

    Abstract The usefulness of a climate-model simulation cannot be inferred solely from its degree of agreement with observations. Instead, one has to consider additional factors such as internal variability, the tuning of the model, observational uncertainty, the temporal change in dominant processes or the uncertainty in the forcing. In any model-evaluation study, the impact of these limiting factors on the suitability of specific metrics must hence be examined. This can only meaningfully be done relative to a given purpose for using a model. I here generally discuss these points and substantiate their impact on model evaluation using the example of sea ice. For this example, I find that many standard metrics such as sea-ice area or volume only permit limited inferences about the shortcomings of individual models.
    Language English
    Publishing date 2015-09-07
    Publishing country England
    Document type Journal Article
    ZDB-ID 208381-4
    ISSN 1471-2962 ; 0080-4614 ; 0264-3820 ; 0264-3952 ; 1364-503X
    ISSN (online) 1471-2962
    ISSN 0080-4614 ; 0264-3820 ; 0264-3952 ; 1364-503X
    DOI 10.1098/rsta.2014.0164
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

    Z 4' 46/25: Show issues
    Z PHI 2: Show issues

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  3. Book ; Online: Revisiting temperature sensitivity

    Nicola, Lena / Notz, Dirk / Winkelmann, Ricarda

    eISSN: 1994-0424

    How does Antarctic precipitation change with temperature?

    2023  

    Abstract: With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate ice-sheet mass losses through increased ice discharge, calving and melting. For sea-level projections it is ... ...

    Abstract With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate ice-sheet mass losses through increased ice discharge, calving and melting. For sea-level projections it is therefore vital to understand the processes determining snowfall changes in Antarctica. Here we revisit the relationship between Antarctic temperature changes and precipitation changes, identifying and explaining regional differences and deviations from the theoretical approach based on the Clausius-Clapeyron relationship. Analysing the latest estimates from global (CMIP6) and regional (RACMO2.3) model projections, we find an average increase of 5.5 % in annual precipitation over Antarctica per degree of warming, with a minimum sensitivity of 2 % K -1 near Siple Coast, and a maximum sensitivity > 10 % K -1 at the East Antarctic Plateau region. This large range can be explained by the prevailing climatic conditions, with local temperatures determining the Clausius-Clapeyron sensitivity that is counteracted in some regions by the prevalence of the coastal wind regime. We compare different approaches of deriving the sensitivity factor, which in some cases can lead to sensitivity changes of up to 7 % for the same model. Importantly, local sensitivity-factors are found to be strongly dependent on the warming level, suggesting that some ice-sheet models which base their precipitation estimates on parameterizations derived from these sensitivity factors might overestimate warming-induced snowfall changes, particularly in high-emission scenarios. This would have consequences for Antarctic sea-level projections for this century and beyond.
    Subject code 910
    Language English
    Publishing date 2023-01-02
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Book ; Online: Revisiting temperature sensitivity

    Nicola, Lena / Notz, Dirk / Winkelmann, Ricarda

    eISSN: 1994-0424

    how does Antarctic precipitation change with temperature?

    2023  

    Abstract: With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate increased ice-sheet mass losses caused by increased ice discharge and melting. For sea-level projections it is ... ...

    Abstract With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate increased ice-sheet mass losses caused by increased ice discharge and melting. For sea-level projections it is therefore vital to understand the processes determining snowfall changes in Antarctica. Here we revisit the relationship between Antarctic temperature changes and precipitation changes, identifying and explaining regional differences and deviations from the theoretical approach based on the Clausius–Clapeyron relationship. Analysing the latest estimates from global (CMIP6, Coupled Model Intercomparison Project Phase 6) and regional (RACMO2.3) model projections, we find an average increase of 5.5 % in annual precipitation over Antarctica per degree of warming, with a minimum sensitivity of 2 % K −1 near Siple Coast and a maximum sensitivity of > 10 % K −1 at the East Antarctic plateau region. This large range can be explained by the prevailing climatic conditions, with local temperatures determining the Clausius–Clapeyron sensitivity that is counteracted in some regions by the prevalence of the coastal wind regime. We compare different approaches of deriving the sensitivity factor, which in some cases can lead to sensitivity changes of up to 7 percentage points for the same model. Importantly, local sensitivity factors are found to be strongly dependent on the warming level, suggesting that some ice-sheet models which base their precipitation estimates on parameterisations derived from these sensitivity factors might overestimate warming-induced snowfall changes, particularly in high-emission scenarios. This would have consequences for Antarctic sea-level projections for this century and beyond.
    Subject code 910
    Language English
    Publishing date 2023-07-03
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Observationally-constrained projections of an ice-free Arctic even under a low emission scenario.

    Kim, Yeon-Hee / Min, Seung-Ki / Gillett, Nathan P / Notz, Dirk / Malinina, Elizaveta

    Nature communications

    2023  Volume 14, Issue 1, Page(s) 3139

    Abstract: The sixth assessment report of the IPCC assessed that the Arctic is projected to be on average practically ice-free in September near mid-century under intermediate and high greenhouse gas emissions scenarios, though not under low emissions scenarios, ... ...

    Abstract The sixth assessment report of the IPCC assessed that the Arctic is projected to be on average practically ice-free in September near mid-century under intermediate and high greenhouse gas emissions scenarios, though not under low emissions scenarios, based on simulations from the latest generation Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Here we show, using an attribution analysis approach, that a dominant influence of greenhouse gas increases on Arctic sea ice area is detectable in three observational datasets in all months of the year, but is on average underestimated by CMIP6 models. By scaling models' sea ice response to greenhouse gases to best match the observed trend in an approach validated in an imperfect model test, we project an ice-free Arctic in September under all scenarios considered. These results emphasize the profound impacts of greenhouse gas emissions on the Arctic, and demonstrate the importance of planning for and adapting to a seasonally ice-free Arctic in the near future.
    Language English
    Publishing date 2023-06-06
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-023-38511-8
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: Atmospheric dynamics: Arctic winds of change

    Notz, Dirk

    Nature climate change

    2016  Volume 6, Issue 9, Page(s) 824

    Language English
    Document type Article
    ZDB-ID 2614383-5
    ISSN 1758-678x
    Database Current Contents Nutrition, Environment, Agriculture

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    In stock of ZB MED Bonn / Germany

    Z 7874: Show issues

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  7. Article: The Trajectory Towards a Seasonally Ice-Free Arctic Ocean.

    Notz, Dirk / Stroeve, Julienne

    Current climate change reports

    2018  Volume 4, Issue 4, Page(s) 407–416

    Abstract: Purpose of review: The observed substantial loss of Arctic sea ice has raised prospects of a seasonally ice-free Arctic Ocean within the foreseeable future. In this review, we summarize our current understanding of the most likely trajectory of the ... ...

    Abstract Purpose of review: The observed substantial loss of Arctic sea ice has raised prospects of a seasonally ice-free Arctic Ocean within the foreseeable future. In this review, we summarize our current understanding of the most likely trajectory of the Arctic sea-ice cover towards this state.
    Recent findings: The future trajectory of the Arctic sea-ice cover can be described through a deterministic component arising primarily from future greenhouse gas emissions, and a chaotic component arising from internal variability. The deterministic component is expected to cause a largely ice-free Arctic Ocean during summer for less than 2
    Summary: The Arctic Ocean will become ice free during summer before mid-century unless greenhouse gas emissions are rapidly reduced.
    Language English
    Publishing date 2018-09-26
    Publishing country Switzerland
    Document type Journal Article ; Review
    ISSN 2198-6061
    ISSN 2198-6061
    DOI 10.1007/s40641-018-0113-2
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Book ; Online: Estimating the uncertainty of sea-ice area and sea-ice extent from satellite retrievals

    Wernecke, Andreas / Notz, Dirk / Kern, Stefan / Lavergne, Thomas

    eISSN:

    2022  

    Abstract: The net Arctic sea-ice area (SIA) can be estimated from the routine monitoring of sea-ice concentration (SIC) by passive microwave measurements from satellites. To be a truly useful metric, for example, of the sensitivity of the Arctic sea-ice cover to ... ...

    Abstract The net Arctic sea-ice area (SIA) can be estimated from the routine monitoring of sea-ice concentration (SIC) by passive microwave measurements from satellites. To be a truly useful metric, for example, of the sensitivity of the Arctic sea-ice cover to global warming, we need, however, reliable estimates of its uncertainty . We here derive this uncertainty by taking spatial and temporal error correlations of the underlying local sea ice concentration products into account. Doing so, we find that the observational uncertainties of both sea-ice area and sea-ice extent (SIE) in 2015 are about 300 000 km 2 for daily and weekly estimates and 160 000 km 2 for monthly estimates. This is about half of the spread in estimated sea-ice area from different passive microwave SIC products, showing that random SIC errors play at least as much a role in SIA uncertainties as inter-SIC-product biases. We further show that the trend of SIA in September, which is traditionally the month with least Arctic sea ice is 105 000 km 2 a -1 ± 9 000 km 2 a -1 for the period from 2002 to 2017. This is the first estimate of a SIA trend with an explicit representation of temporal error correlations.
    Subject code 333 ; 290
    Language English
    Publishing date 2022-11-01
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Book ; Online: Improving model-satellite comparisons of sea ice melt onset with a satellite simulator

    Smith, Abigail / Jahn, Alexandra / Burgard, Clara / Notz, Dirk

    eISSN: 1994-0424

    2022  

    Abstract: Seasonal transitions in Arctic sea ice, such as the melt onset, have been found to be useful metrics for evaluating sea ice in climate models against observations. However, comparisons of melt onset dates between climate models and satellite observations ...

    Abstract Seasonal transitions in Arctic sea ice, such as the melt onset, have been found to be useful metrics for evaluating sea ice in climate models against observations. However, comparisons of melt onset dates between climate models and satellite observations are indirect. Satellite data products of melt onset rely on observed brightness temperatures, while climate models do not currently simulate brightness temperatures, and must therefore define melt onset with other modeled variables. Here we adapt a passive microwave sea ice satellite simulator, the Arctic Ocean Observation Operator (ARC3O), to produce simulated brightness temperatures that can be used to diagnose the timing of the earliest snowmelt in climate models, as we show here using Community Earth System Model version 2 (CESM2) ocean-ice hindcasts. By producing simulated brightness temperatures and earliest snowmelt estimation dates using CESM2 and ARC3O, we facilitate new and previously impossible comparisons between the model and satellite observations by removing the uncertainty that arises due to definition differences. Direct comparisons between the model and satellite data allow us to identify an early bias across large areas of the Arctic at the beginning of the CESM2 ocean-ice hindcast melt season, as well as improve our understanding of the physical processes underlying seasonal changes in brightness temperatures. In particular, the ARC3O allows us to show that satellite algorithm-based melt onset dates likely occur after significant snowmelt has already taken place.
    Subject code 551
    Language English
    Publishing date 2022-08-12
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Article: The Trajectory Towards a Seasonally Ice-Free Arctic Ocean

    Notz, Dirk / Stroeve, Julienne

    Current climate change reports. 2018 Dec., v. 4, no. 4

    2018  

    Abstract: PURPOSE OF REVIEW: The observed substantial loss of Arctic sea ice has raised prospects of a seasonally ice-free Arctic Ocean within the foreseeable future. In this review, we summarize our current understanding of the most likely trajectory of the ... ...

    Abstract PURPOSE OF REVIEW: The observed substantial loss of Arctic sea ice has raised prospects of a seasonally ice-free Arctic Ocean within the foreseeable future. In this review, we summarize our current understanding of the most likely trajectory of the Arctic sea-ice cover towards this state. RECENT FINDINGS: The future trajectory of the Arctic sea-ice cover can be described through a deterministic component arising primarily from future greenhouse gas emissions, and a chaotic component arising from internal variability. The deterministic component is expected to cause a largely ice-free Arctic Ocean during summer for less than 2 ∘C global warming relative to pre-industrial levels. To keep chances below 5 % that the Arctic Ocean will largely be ice free in a given year, total future CO2 emissions must remain below 500 Gt. The Arctic Ocean will become ice free during summer before mid-century unless greenhouse gas emissions are rapidly reduced.
    Keywords carbon dioxide ; global warming ; greenhouse gas emissions ; ice ; summer ; Arctic region
    Language English
    Dates of publication 2018-12
    Size p. 407-416.
    Publishing place Springer International Publishing
    Document type Article
    Note Review
    ISSN 2198-6061
    DOI 10.1007/s40641-018-0113-2
    Database NAL-Catalogue (AGRICOLA)

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