scholarly journals An oceanic perspective on Greenland’s recent freshwater discharge since 1850

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kerstin Perner ◽  
Matthias Moros ◽  
Odd Helge Otterå ◽  
Thomas Blanz ◽  
Ralph R. Schneider ◽  
...  
Keyword(s):  
North Atlantic ◽  
Greenland Ice Sheet ◽  
Arctic Sea Ice ◽  
Freshwater Discharge ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The Past ◽  
Arctic Sea ◽  
Marine Primary Productivity ◽  
Freshwater Release

AbstractInstrumental data evidence an accelerating freshwater release from Arctic sea ice export and the Greenland Ice Sheet over the past three decades causing cooling and freshening in the subpolar North Atlantic region. However, evaluating the observed acceleration on a historical oceanic and climatic perspective remains challenging given the short available instrumental time series. Here we provide a marine perspective on the freshwater releases to the ocean since 1850 as reflected in the northern limb of the Subpolar Gyre. Our reconstructions suggest that the recent acceleration tracks back to the 1940s/50s and is unprecedented since 1850. The melting, initiated by the 1920s natural rise in solar irradiance, accelerated in response to a combined effect of natural and anthropogenic forcing factors. We find that Greenland’s freshwater discharge has contributed to a nutrient-driven fertilization of the upper ocean and consequently increased the marine primary productivity since the 1940s/50s.

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

2009 ◽  
Vol 10 (1) ◽  
pp. 60-78 ◽  
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.

scholarly journals Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial

2012 ◽  
Vol 8 (3) ◽  
pp. 995-1009 ◽  
Author(s):  
P. Bakker ◽  
C. J. Van Meerbeeck ◽  
H. Renssen
Keyword(s):  
North Atlantic ◽  
Deep Convection ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
Summer Temperatures ◽  
The North Atlantic ◽  
The Impact

Abstract. During the Last Interglacial (LIG; ~130 000 yr BP), part of the Greenland Ice Sheet (GIS) melted due to a warmer than present-day climate. However, the impact of this melting on the LIG climate in the North Atlantic region is relatively unknown. Using the LOVECLIM Earth system model of intermediate complexity, we have systematically tested the sensitivity of the LIG climate to increased freshwater runoff from the GIS. In addition, experiments have been performed to investigate the impact of an idealized reduction of both surface elevation and extent of the GIS on the LIG climate. Based on changes in the maximum sea-ice cover and the strength of the overturning circulation, three regimes have been identified, which are characterized by a specific pattern of surface temperature change in the North Atlantic region. By comparing the simulated deep ocean circulation with proxy-based reconstructions, the most realistic simulated climate could be discerned. The resulting climate is characterized by a shutdown of deep convection and a subsequent ~4 °C cooling in the Labrador Sea. Furthermore, a cooling of ~1 °C over the North Atlantic Ocean between 40° N and 70° N is seen. The prescribed reduction in surface elevation and extent of the GIS results in a local warming of up to 4 °C and amplifies the freshwater-forced reduction in deep convection and the resultant cooling in the Nordic Seas. A further comparison of simulated summer temperatures with both continental and oceanic proxy records reveals that the partial melting of the GIS during the LIG could have delayed maximum summer temperatures in the western part of the North Atlantic region relative to the insolation maximum.

scholarly journals Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial

2011 ◽  
Vol 7 (4) ◽  
pp. 2763-2801 ◽  
Author(s):  
P. Bakker ◽  
C. J. Van Meerbeeck ◽  
H. Renssen
Keyword(s):  
North Atlantic ◽  
Deep Convection ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
The North ◽  
Summer Temperatures ◽  
The North Atlantic ◽  
The Impact

Abstract. During the Last Interglacial (LIG; ~130 thousand years BP), part of the Greenland Ice Sheet (GIS) melted under the influence of a warmer than present-day climate. However, the impact of this melting on the LIG climate in the North Atlantic region is unknown. Using the LOVECLIM earth system model of intermediate complexity we have systematically tested the sensitivity of the LIG climate to increased freshwater runoff from the GIS. Moreover, additional experiments have been performed to investigate the impact of an idealized reduction of both altitude and extent of the GIS on the LIG climate. By comparing the simulated deep ocean circulation with proxy-based reconstructions, the most realistic simulated climate could be discerned. The resulting climate is characterized by a shutdown of deep convection in the Labrador Sea and a subsequent cooling here by ~6 °C and ~2 °C over the southern part of Baffin Island and the North Atlantic Ocean between 40° N and 60° N. The reduction of altitude and extent of the GIS results in a local warming of up to 6 °C and a reduction in deep convection and accompanying cooling in the Nordic Seas. Combining model results and proxy-based reconstructions enabled us to constrain the possible melt rate of the GIS to a flux between 0.052 Sv and 0.13 Sv. A further comparison of simulated summer temperatures with both continental and oceanic proxy-records reveals that the partial melting of the GIS during the LIG could have delayed maximum summer temperatures in the western part of the North Atlantic region relative to the insolation maximum.

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