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Fennoscandian freshwater control on Greenland hydroclimate shifts at the onset of the Younger Dryas.

Muschitiello F, Pausata FS, Watson JE, Smittenberg RH, Salih AA, Brooks SJ, Whitehouse NJ, Karlatou-Charalampopoulou A, Wohlfarth B - Nat Commun (2015)

Bottom Line: Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas.The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds.We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas.

View Article: PubMed Central - PubMed

Affiliation: Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, SE-10691 Stockholm, Sweden.

ABSTRACT
Sources and timing of freshwater forcing relative to hydroclimate shifts recorded in Greenland ice cores at the onset of Younger Dryas, ∼12,800 years ago, remain speculative. Here we show that progressive Fennoscandian Ice Sheet (FIS) melting 13,100-12,880 years ago generates a hydroclimate dipole with drier-colder conditions in Northern Europe and wetter-warmer conditions in Greenland. FIS melting culminates 12,880 years ago synchronously with the start of Greenland Stadial 1 and a large-scale hydroclimate transition lasting ∼180 years. Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas. The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds. We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas.

No MeSH data available.


Related in: MedlinePlus

Modelled climate changes under Fennoscandian Ice Sheet freshwater forcing conditions.Summer changes (JJA) in (a) sea-level pressure and (b) sea-ice cover between the 50 years preceding the abrupt cooling (13,000–12,951 model year BP) and the abrupt transition period (12,940–12,891 model year BP). Significance levels are indicated by black stippling (95%). Sites referred to in the text are shown. The areas delimited in red show the location where freshwater forcing was prescribed. Time series of summer (c) sea-level pressure and (d) surface temperature decadal mean (light solid line) anomalies averaged over 57.5°–76.0° N and 20.0°–40.0° W domain for Greenland and 50.0°–65.0° N 5.0°–35.0° E domain for Sweden, respectively. The bold lines show a 50-year running mean. The dotted line represents the end of the modelled Nordic Sea meltwater pulse. Sea-level pressure anomaly changes were estimated after removing the related global mean.
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f4: Modelled climate changes under Fennoscandian Ice Sheet freshwater forcing conditions.Summer changes (JJA) in (a) sea-level pressure and (b) sea-ice cover between the 50 years preceding the abrupt cooling (13,000–12,951 model year BP) and the abrupt transition period (12,940–12,891 model year BP). Significance levels are indicated by black stippling (95%). Sites referred to in the text are shown. The areas delimited in red show the location where freshwater forcing was prescribed. Time series of summer (c) sea-level pressure and (d) surface temperature decadal mean (light solid line) anomalies averaged over 57.5°–76.0° N and 20.0°–40.0° W domain for Greenland and 50.0°–65.0° N 5.0°–35.0° E domain for Sweden, respectively. The bold lines show a 50-year running mean. The dotted line represents the end of the modelled Nordic Sea meltwater pulse. Sea-level pressure anomaly changes were estimated after removing the related global mean.

Mentions: To investigate our hypothesis, we turn to a transient simulation of the last 21,000 years performed with a coupled atmosphere–ocean climate model33 (Methods). The model shows great sensitivity of regional climate to a relatively weak FIS freshwater pulse (0.011 Sv) in the Nordic Seas during the Late AL. The freshwater forcing generates a summer sea-level pressure (SLP) dipole across the North Atlantic with deeper Icelandic low pressure and higher SLP over Northern Europe relative to the preceding phase (Fig. 4). The SLP dipole is a distinct feature in the model and is associated with FIS meltwater forcing only as it is absent when freshwater is discharged from North American sources (Fig. 5). The increased SLP, the surface cooling and the increased sea-ice cover simulated in the Norwegian and Barents Seas (Fig. 4) support the ∼2 °C decline in summer temperatures and progressively drier conditions recorded at HÄ during GI-1a (Fig. 2). These results are consistent with evidence of cooling recorded in other North European records during the same period27. Furthermore, a deeper Icelandic low pressure suggests a closer moisture source for Greenland precipitation, which is consistent with the δ18O enrichment in Greenland ice cores during GI-1a. The model output are further supported by high-resolution δD records from Meerfelder Maar (MFM) in Western Europe17, where relatively wetter conditions are inferred during GI-1a, in contrast to drier conditions in Northern Europe (Supplementary Discussion; Supplementary Fig. 4).


Fennoscandian freshwater control on Greenland hydroclimate shifts at the onset of the Younger Dryas.

Muschitiello F, Pausata FS, Watson JE, Smittenberg RH, Salih AA, Brooks SJ, Whitehouse NJ, Karlatou-Charalampopoulou A, Wohlfarth B - Nat Commun (2015)

Modelled climate changes under Fennoscandian Ice Sheet freshwater forcing conditions.Summer changes (JJA) in (a) sea-level pressure and (b) sea-ice cover between the 50 years preceding the abrupt cooling (13,000–12,951 model year BP) and the abrupt transition period (12,940–12,891 model year BP). Significance levels are indicated by black stippling (95%). Sites referred to in the text are shown. The areas delimited in red show the location where freshwater forcing was prescribed. Time series of summer (c) sea-level pressure and (d) surface temperature decadal mean (light solid line) anomalies averaged over 57.5°–76.0° N and 20.0°–40.0° W domain for Greenland and 50.0°–65.0° N 5.0°–35.0° E domain for Sweden, respectively. The bold lines show a 50-year running mean. The dotted line represents the end of the modelled Nordic Sea meltwater pulse. Sea-level pressure anomaly changes were estimated after removing the related global mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660357&req=5

f4: Modelled climate changes under Fennoscandian Ice Sheet freshwater forcing conditions.Summer changes (JJA) in (a) sea-level pressure and (b) sea-ice cover between the 50 years preceding the abrupt cooling (13,000–12,951 model year BP) and the abrupt transition period (12,940–12,891 model year BP). Significance levels are indicated by black stippling (95%). Sites referred to in the text are shown. The areas delimited in red show the location where freshwater forcing was prescribed. Time series of summer (c) sea-level pressure and (d) surface temperature decadal mean (light solid line) anomalies averaged over 57.5°–76.0° N and 20.0°–40.0° W domain for Greenland and 50.0°–65.0° N 5.0°–35.0° E domain for Sweden, respectively. The bold lines show a 50-year running mean. The dotted line represents the end of the modelled Nordic Sea meltwater pulse. Sea-level pressure anomaly changes were estimated after removing the related global mean.
Mentions: To investigate our hypothesis, we turn to a transient simulation of the last 21,000 years performed with a coupled atmosphere–ocean climate model33 (Methods). The model shows great sensitivity of regional climate to a relatively weak FIS freshwater pulse (0.011 Sv) in the Nordic Seas during the Late AL. The freshwater forcing generates a summer sea-level pressure (SLP) dipole across the North Atlantic with deeper Icelandic low pressure and higher SLP over Northern Europe relative to the preceding phase (Fig. 4). The SLP dipole is a distinct feature in the model and is associated with FIS meltwater forcing only as it is absent when freshwater is discharged from North American sources (Fig. 5). The increased SLP, the surface cooling and the increased sea-ice cover simulated in the Norwegian and Barents Seas (Fig. 4) support the ∼2 °C decline in summer temperatures and progressively drier conditions recorded at HÄ during GI-1a (Fig. 2). These results are consistent with evidence of cooling recorded in other North European records during the same period27. Furthermore, a deeper Icelandic low pressure suggests a closer moisture source for Greenland precipitation, which is consistent with the δ18O enrichment in Greenland ice cores during GI-1a. The model output are further supported by high-resolution δD records from Meerfelder Maar (MFM) in Western Europe17, where relatively wetter conditions are inferred during GI-1a, in contrast to drier conditions in Northern Europe (Supplementary Discussion; Supplementary Fig. 4).

Bottom Line: Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas.The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds.We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas.

View Article: PubMed Central - PubMed

Affiliation: Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, SE-10691 Stockholm, Sweden.

ABSTRACT
Sources and timing of freshwater forcing relative to hydroclimate shifts recorded in Greenland ice cores at the onset of Younger Dryas, ∼12,800 years ago, remain speculative. Here we show that progressive Fennoscandian Ice Sheet (FIS) melting 13,100-12,880 years ago generates a hydroclimate dipole with drier-colder conditions in Northern Europe and wetter-warmer conditions in Greenland. FIS melting culminates 12,880 years ago synchronously with the start of Greenland Stadial 1 and a large-scale hydroclimate transition lasting ∼180 years. Transient climate model simulations forced with FIS freshwater reproduce the initial hydroclimate dipole through sea-ice feedbacks in the Nordic Seas. The transition is attributed to the export of excess sea ice to the subpolar North Atlantic and a subsequent southward shift of the westerly winds. We suggest that North Atlantic hydroclimate sensitivity to FIS freshwater can explain the pace and sign of shifts recorded in Greenland at the climate transition into the Younger Dryas.

No MeSH data available.


Related in: MedlinePlus