North Atlantic region atmospheric circulation dynamics inferred from a late-Holocene lacustrine carbonate isotope record, northern Swedish Lapland

The Holocene ◽  
2007 ◽  
Vol 17 (7) ◽  
pp. 867-873 ◽  
Author(s):  
Gunhild C. Rosqvist ◽  
Melanie J. Leng ◽  
Christina Jonsson
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Late Holocene ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Isotope Record ◽  
Lacustrine Carbonate ◽  
Circulation Dynamics

scholarly journals Solar and volcanic forcing of North Atlantic climate inferred from a process-based reconstruction

2018 ◽  
Vol 14 (8) ◽  
pp. 1179-1194 ◽  
Author(s):  
Jesper Sjolte ◽  
Christophe Sturm ◽  
Florian Adolphi ◽  
Bo M. Vinther ◽  
Martin Werner ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Volcanic Eruptions ◽  
North Atlantic Region ◽  
Solar Forcing ◽  
Atlantic Region ◽  
The North ◽  
External Forcings ◽  
Pressure Anomaly ◽  
The North Atlantic

Abstract. The effect of external forcings on atmospheric circulation is debated. Due to the short observational period, the analysis of the role of external forcings is hampered, making it difficult to assess the sensitivity of atmospheric circulation to external forcings, as well as persistence of the effects. In observations, the average response to tropical volcanic eruptions is a positive North Atlantic Oscillation (NAO) during the following winter. However, past major tropical eruptions exceeding the magnitude of eruptions during the instrumental era could have had more lasting effects. Decadal NAO variability has been suggested to follow the 11-year solar cycle, and linkages have been made between grand solar minima and negative NAO. However, the solar link to NAO found by modeling studies is not unequivocally supported by reconstructions, and is not consistently present in observations for the 20th century. Here we present a reconstruction of atmospheric winter circulation for the North Atlantic region covering the period 1241–1970 CE. Based on seasonally resolved Greenland ice core records and a 1200-year-long simulation with an isotope-enabled climate model, we reconstruct sea level pressure and temperature by matching the spatiotemporal variability in the modeled isotopic composition to that of the ice cores. This method allows us to capture the primary (NAO) and secondary mode (Eastern Atlantic Pattern) of atmospheric circulation in the North Atlantic region, while, contrary to previous reconstructions, preserving the amplitude of observed year-to-year atmospheric variability. Our results show five winters of positive NAO on average following major tropical volcanic eruptions, which is more persistent than previously suggested. In response to decadal minima of solar activity we find a high-pressure anomaly over northern Europe, while a reinforced opposite response in pressure emerges with a 5-year time lag. On centennial timescales we observe a similar response of circulation as for the 5-year time-lagged response, with a high-pressure anomaly across North America and south of Greenland. This response to solar forcing is correlated to the second mode of atmospheric circulation, the Eastern Atlantic Pattern. The response could be due to an increase in blocking frequency, possibly linked to a weakening of the subpolar gyre. The long-term anomalies of temperature during solar minima shows cooling across Greenland, Iceland and western Europe, resembling the cooling pattern during the Little Ice Age (1450–1850 CE). While our results show significant correlation between solar forcing and the secondary circulation pattern on decadal (r=0.29, p<0.01) and centennial timescales (r=0.6, p<0.01), we find no consistent relationship between solar forcing and NAO. We conclude that solar and volcanic forcing impacts different modes of our reconstructed atmospheric circulation, which can aid in separating the regional effects of forcings and understanding the underlying mechanisms.

scholarly journals Is there evidence for a 4.2 ka BP event in the northern North Atlantic region?

2019 ◽  
Author(s):  
Raymond Bradley ◽  
Jostein Bakke
Keyword(s):  
North Atlantic ◽  
Late Holocene ◽  
Climatic Conditions ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
General Decline ◽  
The World ◽  
Local Manifestation ◽  
Paleoclimatic Records ◽  
Glacial Advance

Abstract. We review paleoceanographic and paleoclimatic records from the northern North Atlantic to assess the nature of climatic conditions at 4.2 ka BP, which has been identified as a time of exceptional climatic anomalies in many parts of the world. The northern North Atlantic region experienced relatively warm conditions in the early Holocene (6–8 ka BP) followed by a general decline in temperatures after ~ 5 ka BP, which led to the onset of Neoglaciation. Although a few records do show a distinct anomaly around 4.2 ka BP (associated with a glacial advance), this is not widespread and we interpret it as a local manifestation of the overall climatic deterioration that characterizes the late Holocene.

scholarly journals Is there evidence for a 4.2 ka BP event in the northern North Atlantic region?

2019 ◽  
Vol 15 (5) ◽  
pp. 1665-1676 ◽  
Author(s):  
Raymond S. Bradley ◽  
Jostein Bakke
Keyword(s):  
North Atlantic ◽  
Late Holocene ◽  
Climatic Conditions ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
General Decline ◽  
The World ◽  
Paleoclimatic Records ◽  
Glacial Advance

Abstract. We review paleoceanographic and paleoclimatic records from the northern North Atlantic to assess the nature of climatic conditions at 4.2 ka BP, which has been identified as a time of exceptional climatic anomalies in many parts of the world. The northern North Atlantic region experienced relatively warm conditions from 6 to 8 ka BP, followed by a general decline in temperatures after ∼5 ka BP, which led to the onset of neoglaciation. Over the last 5000 years, a series of multi-decadal- to century-scale fluctuations occurred, superimposed on an overall decline in temperature. Although a few records do show a glacial advance around 4.2 ka BP, because they are not widespread we interpret them as local events – simply one glacial advance of many that occurred in response to the overall climatic deterioration that characterized the late Holocene.

scholarly journals Decadal Variability in a Central Greenland High-Resolution Deuterium Isotope Record and Its Relationship to the Frequency of Daily Atmospheric Circulation Patterns from the North Atlantic Region

2010 ◽  
Vol 23 (17) ◽  
pp. 4608-4618 ◽  
Author(s):  
Norel Rimbu ◽  
Gerrit Lohmann
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Decadal Variability ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Circulation Patterns ◽  
Isotope Record ◽  
The North Atlantic

Abstract The variability of an annual resolution deuterium time series from central Greenland is investigated in connection with the variability in the frequency of daily atmospheric circulation patterns in the North Atlantic region. Statistical analysis reveals that a large part of the decadal variability of the deuterium isotope record is related to decadal variability in the frequency of several identified daily circulation patterns. The study shows that these circulation patterns induce variations in the deuterium record by altering where isotopic fractionation occurs, mainly during the passage of the associated air masses over continental areas. The study identifies three significant periodic components in the deuterium isotope record at ∼12, ∼20, and ∼30 yr. It also shows that the ∼20-yr signal in the deuterium isotope record is related to the variability in the frequency of a winter circulation type. An analysis of six oxygen isotope records from central Greenland reveals decadal variations similar to the deuterium isotope record. The authors argue that high-resolution stable isotope records from Greenland ice cores can be used to obtain information about the frequency of certain daily circulation patterns during past periods.

scholarly journals Solar and volcanic forcing of North Atlantic climate inferred from a process-based reconstruction

2018 ◽  
Author(s):  
Jesper Sjolte ◽  
Christophe Sturm ◽  
Florian Adolphi ◽  
Bo M. Vinther ◽  
Martin Werner ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Volcanic Eruptions ◽  
Similar Response ◽  
North Atlantic Region ◽  
Solar Forcing ◽  
Atlantic Region ◽  
The North ◽  
External Forcings ◽  
The North Atlantic

Abstract. External forcings are known to impact atmospheric circulation. However, the analysis of the role of external forcings based on observational data is hampered due to the short observational period, and the sensitivity of atmospheric circulation to external forcings as well as persistence the effects are debated. A positive phase of the North Atlantic Oscillation (NAO) has been observed the following winter after tropical volcanic eruptions. However, past major tropical eruptions exceeding the magnitude of eruptions during the instrumental era could have more lasting effects. Decadal NAO variability has been suggested to follow the 11-year solar cycle, and linkages has been made between grand solar minima and negative NAO. However, the solar link to NAO found by modeling studies is not unequivocally supported by reconstructions, and is not consistently present in observations for the 20th century. Here we present a reconstruction of atmospheric winter circulation for the North Atlantic region covering the period 1241–1970 CE. Based on seasonally resolved Greenland ice core records and a 1200-year long simulation with an isotope enabled climate model, we reconstruct sea level pressure and temperature by matching the spatio-temporal variability of the modeled isotopic composition to that of the ice cores. This method allows us to capture the primary and secondary modes of atmospheric circulation in the North Atlantic region, while, contrary to previous reconstructions, preserving the amplitude of observed year-to-year atmospheric variability. Our results show 5 winters of positive NAO on average following major tropical volcanic eruptions, which is more persistent than previously suggested. In response to decadal minima of solar activity we find a high-pressure anomaly over Northern Europe, while a reinforced opposite response in pressure emerges with a 5-year time lag. On longer time scales we observe a similar response in circulation as for the 5-year time-lagged response. This is likely due to an increase in blocking frequency and an associated weakening of the subpolar gyre. The long-term response of temperature to solar minima shows cooling across Greenland, Iceland and Western Europe, resembling the cooling pattern during the Little Ice Age. While our results show a clear link between solar forcing and the secondary circulation patterns, we find no consistent relationship between solar forcing and NAO.

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