Simulated winter circulation types in the North Atlantic and European region for preindustrial and glacial conditions

Hofer, Dominik; Raible, Christoph C.; Merz, Niklaus; Dehnert, Andreas; Kuhlemann, Joachim

doi:10.1029/2012gl052296

Cited by 41 publications

(47 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Daily LGM patterns are also in agreement with PD (0.65 ≤ r PD-LGM ≤ 0.94). This means that although the NH atmospheric circulation during the LGM strongly differs from the present-day conditions (Hofer et al, 2012b), the relative daily weather patterns (anomalies from the seasonal means) that lead to precipitation over any of the three Greenland regions largely remain the same.…”

Section: Stability During Past Climate Statesmentioning

confidence: 99%

Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleoclimate simulations

Merz

Raible²,

Fischer³

et al. 2013

Clim. Past

Self Cite

View full text Add to dashboard Cite

Abstract. Changes in Greenland accumulation and the stability in the relationship between accumulation variability and large-scale circulation are assessed by performing timeslice simulations for the present day, the preindustrial era, the early Holocene, and the Last Glacial Maximum (LGM) with a comprehensive climate model. The stability issue is an important prerequisite for reconstructions of Northern Hemisphere atmospheric circulation variability based on accumulation or precipitation proxy records from Greenland ice cores. The analysis reveals that the relationship between accumulation variability and large-scale circulation undergoes a significant seasonal cycle. As the contributions of the individual seasons to the annual signal change, annual mean accumulation variability is not necessarily related to the same atmospheric circulation patterns during the different climate states. Interestingly, within a season, local Greenland accumulation variability is indeed linked to a consistent circulation pattern, which is observed for all studied climate periods, even for the LGM. Hence, it would be possible to deduce a reliable reconstruction of seasonal atmospheric variability (e.g., for North Atlantic winters) if an accumulation or precipitation proxy were available that resolves single seasons. We further show that the simulated impacts of orbital forcing and changes in the ice sheet topography on Greenland accumulation exhibit strong spatial differences, emphasizing that accumulation records from different ice core sites regarding both interannual and long-term (centennial to millennial) variability cannot be expected to look alike since they include a distinct local signature. The only uniform signal to external forcing is the strong decrease in Greenland accumulation during glacial (LGM) conditions and an increase associated with the recent rise in greenhouse gas concentrations.

show abstract

Section: Stability During Past Climate Statesmentioning

confidence: 99%

Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleoclimate simulations

Merz

Raible²,

Fischer³

et al. 2013

Clim. Past

Self Cite

View full text Add to dashboard Cite

show abstract

“…The same is true for accumulation which requires knowing patterns of rainfall and temperature. Since LGM 20 climate is known to have behaved rather differently from today owing to the southward displacement of the atmospheric polar front in the North Atlantic (Florineth, 1998;Hofer et al, 2012;Luetscher et al, 2015), it is questionable whether the added complexity of a PDD model results in a more accurate representation of LGM mass balance distribution. glacier (Haeberli and Penz, 1985) or with present-day Greenland values (Machguth et al, 2016) measured in regions where temperatures and precipitation are similar to estimated LGM conditions in northern Switzerland.…”

mentioning

confidence: 99%

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

Cohen¹,

Gillet-Chaulet²,

Haeberli³

et al. 2017

Preprint

View full text Add to dashboard Cite

Abstract. At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16,000 km 2 .As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a fully-coupled, three-dimensional, transient, thermo-mechanical Stokes flow model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold (T July ∼ 0 • C at the glacier terminus) and dry (∼ 10 5 to 20% of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions.Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs ). In the lobes, despite low surface slopes and low basal shear stresses, sliding dictated main fluxes of ice which closely followed bedrock topography: ice was channeled in between bedrock highs along troughs, some of which coincided with glacially eroded overdeepenings. These sliding conditions may have favored glacial erosion by abrasion and quarrying. 20Our results confirmed general earlier findings but provided more insights into the detailed flow and basal conditions of the Rhine glacier at the LGM. Our model results suggested that the trimline could have been buried by a significant thickness of cold ice. These findings have significant implications for interpreting trimlines in the Alps and for our understanding of ice-climate interactions.

show abstract

“…Two metrics have been used for assignation: the Spearman correlation and the Euclidean distance. The former measures the spatial similarity of two fields (Hofer et al, 2012;Vautard and Yiou, 2009), whereas the latter evaluates the differences in the intensity of patterns (Fettweis et al, 2011). Both metrics are relevant and complementary (Nogaj et al, 2007;Fettweis et al, 2011).…”

Section: Allocation Methodsmentioning

confidence: 99%

Attributing trends in extremely hot days to changes in atmospheric dynamics

García‐Valero

Montávez

Gómez-Navarro

et al. 2015

Nat. Hazards Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. This paper presents a method for attributing regional trends in the frequency of extremely hot days (EHDs) to changes in the frequency of the atmospheric patterns that characterize such extraordinary events. The study is applied to mainland Spain and the Balearic Islands for the extended summers of the period 1958-2008, where significant and positive trends in maximum temperature (T x ) have been reported during the second half of the past century.First, the study area was split into eight regions attending to their different temporal variability of the daily T x series obtained from the Spain02 gridded data set using a clustering procedure. Second, the large-scale atmospheric situations causing EHDs are defined by circulation types (CTs). The obtainment of the CTs differs from the majority of CT classifications proposed in the literature. It is based on regional series and on a previous characterization of the main atmospheric situations obtained using only some days classified as extremes in the different regions. Three different atmospheric fields (SLP, T850, and Z500) from ECMWF reanalysis and analysis data and combinations of them (SLP-T850, SLP-Z500, and T850-Z500) are used to produce six different CT classifications. Subsequently, links between EHD occurrence in the different regions and CT for all days have been established. Finally, a simple model to relate the trends in EHDs for each region to the changes in the CT frequency appearance has been formulated.Most regions present positive and significant trends in the occurrence of EHDs. The CT classifications using two variables perform better. In particular, SLP-T850 is the best for characterizing the atmospheric situations leading to EHD occurrences for most of the regions. Only a small number of CTs have significant trends in their frequency and are associated with high efficiency causing EHD occurrences in most regions simultaneously, especially in the northern and central regions. Attribution results show that changes in circulation can only explain some part of the regional EHD trends. The percentage of the trend attributable to changes in atmospheric dynamics varies from 15 to 50 %, depends on the region and is sensitive to the selected large-scale variables.

show abstract

Simulated winter circulation types in the North Atlantic and European region for preindustrial and glacial conditions

Cited by 41 publications

References 21 publications

Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleoclimate simulations

Greenland accumulation and its connection to the large-scale atmospheric circulation in ERA-Interim and paleoclimate simulations

Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum

Attributing trends in extremely hot days to changes in atmospheric dynamics

Contact Info

Product

Resources

About