The North Atlantic Oscillation and the Greenland ice sheet in CMIP6

<div>The North Atlantic Oscillation (NAO) is an important control on both northern European weather and Greenland ice sheet surface mass budget via the path of storm tracks that deliver precipitation, particularly in the winter, and by the strength and persistence of the Greenland blocking high that promotes melt in summer. Within CMIP5 models, atmospheric blocking was generally poorly represented regardless of location, we here examine an ensemble of 10 CMIP6 fully coupled earth system models (ESMs) that were available by Summer 2019 in order to examine if model improvements better represent the NAO in CMIP6.</div><div>We examine&#160;&#160;temperature over Greenland and the north Atlantic region as well as NAO position, persistence and strength in winter and summer for each model in the historical scenario. No single model performs well on all characteristics but the UKESM and EC-EARTH3 perform the best when compared to the ERA5 climate reanalysis.</div><div>We also show how the NAO is expected to change in&#160;8 of these&#160;models under different future climate scenarios.&#160;&#160;The location&#160;of the Icelandic low in particular migrates northwards by varying amounts, likely related to Arctic sea ice changes within the models and with a consequent impact on precipitation.</div><div>Downscaling experiments carried out using the HIRHAM5 regional climate model over the Greenland ice sheet show the importance of accurately characterising the NAO in order to correctly&#160;&#160;estimate both winter accumulation and summer melt and the combination that gives the ice sheet mass budget. Our study emphasises the importance of assessing a range of different climate and weather variables when selecting models to downscale for&#160;obtaining&#160;ice sheet mass balance. We also note that while some progress has been made in&#160;better representing atmospheric blocking in ESMs, largely down to higher resolution in atmospheric models, there is still a substantial improvement required before ESMs can be said to accurately characterise the climate of the North Atlantic region with consequent impacts on ice sheet surface mass budget projections.</div>

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The Occurrence and Properties of Long-Lived Liquid-Bearing Clouds over the Greenland Ice Sheet and Their Relationship to the North Atlantic Oscillation

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0230.1 ◽

2018 ◽

Vol 57 (4) ◽

pp. 921-935 ◽

Cited By ~ 4

Author(s):

Jonathan Edwards-Opperman ◽

Steven Cavallo ◽

David Turner

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

The Arctic ◽

Positive Phase ◽

Cloud Base ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

AbstractStratiform liquid-bearing clouds (LBCs), defined herein as either pure liquid or mixed-phase clouds, have a large impact on the surface radiation budget across the Arctic. LBCs lasting at least 6 h are observed at Summit, Greenland, year-round with a maximum in occurrence during summer. Mean cloud-base height is below 1 km for 85% of LBC cases identified, 59% have mean liquid water path (LWP) values between 10 and 40 g m−2, and most produce sporadic light ice-phase precipitation. During their occurrence, the atmosphere above the ice sheet is anomalously warm and moist, with southerly winds observed over much of the ice sheet, including at Summit. LBCs that occur when the North Atlantic Oscillation (NAO) is in the negative phase correspond to strong ridging centered over the Greenland Ice Sheet (GIS), allowing for southwesterly flow over the GIS toward Summit. During the positive phase of the NAO, the occurrence of LBCs corresponds to a cyclone located off the southeastern coast of the ice sheet, which leads to easterly-to-southeasterly flow toward Summit. Furthermore, air parcels at Summit frequently originate from below the elevation of Summit, indicating that orographic lift along the ice sheet is a factor in the occurrence of LBCs at Summit. LBCs are more frequently observed during the negative NAO, and both the LWP and precipitation rate are larger in LBCs occurring during this phase. Mean LWP in LBCs occurring during the negative NAO is 15 g m−2 larger than in LBCs occurring during the positive phase.

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Small impact of surrounding oceanic conditions on 2007–2012 Greenland Ice Sheet surface mass balance

The Cryosphere Discussions ◽

10.5194/tcd-8-1453-2014 ◽

2014 ◽

Vol 8 (2) ◽

pp. 1453-1477 ◽

Cited By ~ 2

Author(s):

B. Noël ◽

X. Fettweis ◽

W. J. van de Berg ◽

M. R. van den Broeke ◽

M. Erpicum

Keyword(s):

Mass Balance ◽

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

Katabatic Winds ◽

Surface Mass ◽

The North ◽

The North Atlantic ◽

Surface Melt

Abstract. During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS.

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Synoptic Forcing of Precipitation over Greenland: Climatology for 1961–99

Journal of Hydrometeorology ◽

10.1175/2008jhm1014.1 ◽

2009 ◽

Vol 10 (1) ◽

pp. 60-78 ◽

Cited By ~ 52

Author(s):

Keah C. Schuenemann ◽

John J. Cassano ◽

Joel Finnis

Keyword(s):

North Atlantic ◽

Winter Season ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Synoptic Climatology ◽

North Atlantic Region ◽

Atlantic Region ◽

Synoptic Patterns ◽

The North ◽

The North Atlantic

Abstract Analysis of the synoptic climatology and precipitation patterns over the North Atlantic region allows for a better understanding of the atmospheric input to the mass balance of the Greenland ice sheet. The self-organizing map (SOM) technique was applied to the 40-yr European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40) daily sea level pressure (SLP) data from 1961 to 1999 to objectively identify synoptic SLP patterns over the North Atlantic region. A total of 35 different SLP patterns were identified. Patterns common to the winter season are characterized by deep low pressure systems that approach Greenland through an active North Atlantic storm track, whereas patterns most common to the summer months are generally weaker and approach the ice sheet from the west through Baffin Bay. The blocking, splitting, and intensification of cyclones by the high elevations of the Greenland ice sheet were identified in this analysis. Analysis of ERA-40 precipitation associated with each SLP pattern revealed that the largest precipitation events were associated with passing cyclones that created onshore flow, allowing the air to be lifted orographically by the steep margins of the ice sheet. The ERA-40 annual mean precipitation over Greenland from 1961 to 1999 was 35.8 cm yr−1. Greenland was divided into five subregions, and the preferred synoptic patterns for receiving precipitation in each region include cyclones positioned to allow dynamic and orographic lift in each region. Annual precipitation contributions from each SLP pattern were isolated to reveal that half of the annual mean precipitation over Greenland comes from only 11 of the 35 identified synoptic patterns (31.4%), highlighting the importance of studying Greenland precipitation on an event-by-event basis on a daily time scale.

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Link between the North Atlantic Oscillation and the surface mass balance components of the Greenland Ice Sheet under preindustrial and last interglacial climates: a study with a coupled global circulation model

Climate of the Past ◽

10.5194/cp-14-1707-2018 ◽

2018 ◽

Vol 14 (11) ◽

pp. 1707-1725

Author(s):

Silvana Ramos Buarque ◽

David Salas y Melia

Keyword(s):

North Atlantic ◽

Greenland Ice Sheet ◽

Negative Phase ◽

Surface Mass Balance ◽

Last Interglacial ◽

Surface Mass ◽

The North ◽

Nao Index ◽

The North Atlantic ◽

The North Atlantic Oscillation

Abstract. The relationship between the surface mass balance (SMB) components (accumulation and melting) of the Greenland Ice Sheet (GrIS) and the North Atlantic Oscillation (NAO) is examined from numerical simulations performed with a new atmospheric stretched grid configuration of the Centre National de Recherches Météorologiques Coupled Model (CNRM-CM) version 5.2 under three periods: preindustrial climate, a warm phase (early Eemian, 130 ka BP) and a cool phase (late Eemian, 115 ka BP) of the last interglacial. The horizontal grid of the atmospheric component of CNRM-CM5.2 is stretched from the tilted pole on Baffin Bay (72∘ N, 65∘ W) in order to obtain a higher spatial resolution on Greenland. The correlation between simulated SMB anomalies averaged over Greenland and the NAO index is weak in winter and significant in summer (about 0.6 for the three periods). In summer, spatial correlations between the NAO index and SMB components display different patterns from one period to another. These differences are analyzed in terms of the respective influence of the positive and negative phases of the NAO on accumulation and melting. Accumulation in south Greenland is significantly correlated with the positive (negative) phase of the NAO in a warm (cold) climate. Under preindustrial and 115 ka BP climates, melting along the margins is more correlated with the positive phase of the NAO than with its negative phase, whereas at 130 ka BP it is more correlated with the negative phase of the NAO in north and northeast Greenland.

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Sensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR

The Cryosphere ◽

10.5194/tc-8-1871-2014 ◽

2014 ◽

Vol 8 (5) ◽

pp. 1871-1883 ◽

Cited By ~ 38

Author(s):

B. Noël ◽

X. Fettweis ◽

W. J. van de Berg ◽

M. R. van den Broeke ◽

M. Erpicum

Keyword(s):

North Atlantic ◽

Climate Model ◽

Regional Climate ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Sea Surface ◽

Surface Mass ◽

The North ◽

The North Atlantic ◽

Sst Anomalies

Abstract. During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS.

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The North Atlantic Oscillation signature in deuterium and deuterium excess signals in the Greenland Ice Sheet Project 2 Ice Core, 1840-1970

Geophysical Research Letters ◽

10.1029/93gl03305 ◽

1993 ◽

Vol 20 (24) ◽

pp. 2901-2904 ◽

Cited By ~ 86

Author(s):

L. K. Barlow ◽

J. W. C. White ◽

R. G. Barry ◽

J. C. Rogers ◽

P. M. Grootes

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Ice Core ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Deuterium Excess ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

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Link between the Surface Mass Balance of the Greenland Ice Sheet and the North Atlantic Oscillation under preindustrial and last interglacial climates: a study with a Coupled Global Circulation Model

10.5194/cp-2018-12 ◽

2018 ◽

Author(s):

Silvana Ramos Buarque ◽

David Salas y Melia

Keyword(s):

North Atlantic ◽

Greenland Ice Sheet ◽

Negative Phase ◽

Surface Mass Balance ◽

Last Interglacial ◽

Surface Mass ◽

The North ◽

Nao Index ◽

The North Atlantic ◽

The North Atlantic Oscillation

Abstract. The relationship between the Surface Mass Balance (SMB) of the Greenland Ice Sheet (GrIS) and the North Atlantic Oscillation (NAO) is examined from numerical simulations performed with a new atmospheric stretched grid configuration of the Centre National de Recherches Météorologiques – Coupled Model (CNRM-CM) version 5.2 under three periods : preindustrial climate, a warm phase (early Eemian, 130 ka BP) and a cool phase (glacial inception, 115 ka BP) of the last interglacial. The horizontal grid of the atmospheric component of CNRM-CM5.2 is stretched from the tilted pole on the Baffin Bay (72° N, 65° W) in order to obtain a higher spatial resolution on Greenland. The correlation between simulated SMB anomalies averaged over Greenland and the NAO index is weak in winter and significant in summer (about 0.6 for the three periods). In summer, spatial correlations between the NAO index and SMB display different patterns from one period to another. These differences are analysed in terms of the respective influence of the positive and negative phases of the NAO on accumulation and melting. Accumulation in South Greenland is significantly correlated with the positive (negative) phase of the NAO in a warm (cold) climate. Under preindustrial and 115 ka climates, melting along the margins is more correlated with the positive phase of the NAO than with its negative phase, whereas at 130 ka it is more correlated with the negative phase of the NAO in North and North-East Greenland.

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Greenland melting signatures in model simulations and oceanic observations

10.5194/egusphere-egu21-8225 ◽

2021 ◽

Author(s):

Sophie Stolzenberger ◽

Roelof Rietbroek ◽

Claudia Wekerle ◽

Bernd Uebbing ◽

Jürgen Kusche

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ocean Model ◽

Freshwater Flux ◽

Model Simulations ◽

The North ◽

Sea Level Anomalies ◽

The North Atlantic ◽

The Impact

The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.

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On the role of atmospheric feedbacks in sustaining the anomalous warmth of the MIS-11 interglacial

10.5194/egusphere-egu21-7316 ◽

2021 ◽

Author(s):

Brian Crow ◽

Matthias Prange ◽

Michael Schulz

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Meridional Overturning Circulation ◽

Interglacial Period ◽

Climate Modelling ◽

Ice Dynamics ◽

The North ◽

Atmospheric Feedbacks ◽

The North Atlantic

Historical estimates of the melt rate and extent of the Greenland ice sheet (GrIS) are poorly constrained, due both to incomplete understanding of relevant ice dynamics and the magnitude of forcing acting upon the ice sheet (e.g., Alley et al. 2010). Previous assessments of the Marine Isotope Stage 11 (MIS-11) interglacial period have determined it was likely one of the warmest and longest interglacial periods of the past 800 kyr, leading to melt of at least half the present-day volume of the Greenland ice sheet (Robinson et al. 2017). An enhanced Atlantic meridional overturning circulation (AMOC) is commonly cited as sustaining the anomalous warmth across the North Atlantic and Greenland (e.g., Rachmayani et al. 2017), but little is known about potential atmospheric contributions. Paleorecords from this period are sparse, and detailed climate modelling studies of this period have been heretofore very limited. The climatic conditions over Greenland and the North Atlantic region, and how they may have contributed to the melt of the GrIS during MIS-11, are therefore not well understood. By utilizing climate simulations with the Community Earth System Model (CESM), our study indicates that changes in atmospheric eddy behavior, including eddy fluxes of heat and precipitation, made significant contributions to the negative mass balance conditions over the GrIS during the MIS-11 interglacial. Thus, accounting for the effects of atmospheric feedbacks in a warmer-than-present climate is a necessary component for future analyses attempting to better constrain the extent and rate of melt of the GrIS.

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