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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

Paleoclimate proxy data from Hässeldala and the Greenland ice core record.δD values of (a) n-C21 (aquatic plants δDaq; blue) and weighted average of δD values of n-C27–29–31 based on relative n-alkane abundances (higher terrestrial plants δDterr; green), as well as (b) terrestrial evapotranspiration (ΔδDterr-aq) and (c) chironomid-based summer temperatures during the regional YD pollen zone at Hässeldala compared to (d,e) the NGRIP δ18O record21. The NGRIP record is plotted both on its original time scale and on the IntCal13 time scale (see text for details) after synchronization between the ice-core 10Be and tree-ring 14C time scales20. Beyond 13,500 years BP, which is the limit of the synchronization between the time scales, we reset the GICC05 cumulative counting error21. Red triangles denote 14C chronological constraints used in the final age-depth model. All records are presented with shadings indicating empirical 95% uncertainty bounds based on analytical and age-model errors. The Hässeldala pollen stratigraphy and Greenland climate events based on the GICC05 (after converting b2k age to BP) are indicated at the top and in the bottom, respectively. The timing of the major excursion in δDaq values at 13090±37 year BP was estimated using a Bayesian change point procedure45.
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f2: Paleoclimate proxy data from Hässeldala and the Greenland ice core record.δD values of (a) n-C21 (aquatic plants δDaq; blue) and weighted average of δD values of n-C27–29–31 based on relative n-alkane abundances (higher terrestrial plants δDterr; green), as well as (b) terrestrial evapotranspiration (ΔδDterr-aq) and (c) chironomid-based summer temperatures during the regional YD pollen zone at Hässeldala compared to (d,e) the NGRIP δ18O record21. The NGRIP record is plotted both on its original time scale and on the IntCal13 time scale (see text for details) after synchronization between the ice-core 10Be and tree-ring 14C time scales20. Beyond 13,500 years BP, which is the limit of the synchronization between the time scales, we reset the GICC05 cumulative counting error21. Red triangles denote 14C chronological constraints used in the final age-depth model. All records are presented with shadings indicating empirical 95% uncertainty bounds based on analytical and age-model errors. The Hässeldala pollen stratigraphy and Greenland climate events based on the GICC05 (after converting b2k age to BP) are indicated at the top and in the bottom, respectively. The timing of the major excursion in δDaq values at 13090±37 year BP was estimated using a Bayesian change point procedure45.

Mentions: The HÄ δDaq and ΔδDterr−aq records show a remarkable two-step decrease and increase, respectively, starting shortly before the onset of the YD as defined in the pollenstratigraphy11 (Fig. 2). Similarly, after a ∼300-year long summer warming of up to 4 °C during the Allerød pollen zone (AL), chironomid–inferred temperatures indicate a prominent two-step cooling preceding the start of the YD (Fig. 2). In the first step δDaq values start to decrease by 25‰ at 13,090±37 year BP (±1σ) and reach an isotopic minimum at 12,883±35 year BP. This δDaq decline coincides with a 27‰ rise in ΔδDterr-aq, peaking at 12,883±35 year BP, and a ∼2 °C decrease in summer temperatures (Fig. 2), suggesting substantially drier and colder summer conditions. After a brief recovery, a second step occurs. At 12,700±52 year BP, δDaq values decrease again by at least 34‰. The drop in δDaq values straddles the pollen–stratigraphic AL–YD transition, which is a regional marker for major environmental changes resulted from hemispheric-scale cooling27 (Fig. 2). This shift coincides with a 26‰ rise in ΔδDterr-aq and a ∼3 °C decrease in summer temperatures, indicating a further change towards drier and colder summer conditions.


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)

Paleoclimate proxy data from Hässeldala and the Greenland ice core record.δD values of (a) n-C21 (aquatic plants δDaq; blue) and weighted average of δD values of n-C27–29–31 based on relative n-alkane abundances (higher terrestrial plants δDterr; green), as well as (b) terrestrial evapotranspiration (ΔδDterr-aq) and (c) chironomid-based summer temperatures during the regional YD pollen zone at Hässeldala compared to (d,e) the NGRIP δ18O record21. The NGRIP record is plotted both on its original time scale and on the IntCal13 time scale (see text for details) after synchronization between the ice-core 10Be and tree-ring 14C time scales20. Beyond 13,500 years BP, which is the limit of the synchronization between the time scales, we reset the GICC05 cumulative counting error21. Red triangles denote 14C chronological constraints used in the final age-depth model. All records are presented with shadings indicating empirical 95% uncertainty bounds based on analytical and age-model errors. The Hässeldala pollen stratigraphy and Greenland climate events based on the GICC05 (after converting b2k age to BP) are indicated at the top and in the bottom, respectively. The timing of the major excursion in δDaq values at 13090±37 year BP was estimated using a Bayesian change point procedure45.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Paleoclimate proxy data from Hässeldala and the Greenland ice core record.δD values of (a) n-C21 (aquatic plants δDaq; blue) and weighted average of δD values of n-C27–29–31 based on relative n-alkane abundances (higher terrestrial plants δDterr; green), as well as (b) terrestrial evapotranspiration (ΔδDterr-aq) and (c) chironomid-based summer temperatures during the regional YD pollen zone at Hässeldala compared to (d,e) the NGRIP δ18O record21. The NGRIP record is plotted both on its original time scale and on the IntCal13 time scale (see text for details) after synchronization between the ice-core 10Be and tree-ring 14C time scales20. Beyond 13,500 years BP, which is the limit of the synchronization between the time scales, we reset the GICC05 cumulative counting error21. Red triangles denote 14C chronological constraints used in the final age-depth model. All records are presented with shadings indicating empirical 95% uncertainty bounds based on analytical and age-model errors. The Hässeldala pollen stratigraphy and Greenland climate events based on the GICC05 (after converting b2k age to BP) are indicated at the top and in the bottom, respectively. The timing of the major excursion in δDaq values at 13090±37 year BP was estimated using a Bayesian change point procedure45.
Mentions: The HÄ δDaq and ΔδDterr−aq records show a remarkable two-step decrease and increase, respectively, starting shortly before the onset of the YD as defined in the pollenstratigraphy11 (Fig. 2). Similarly, after a ∼300-year long summer warming of up to 4 °C during the Allerød pollen zone (AL), chironomid–inferred temperatures indicate a prominent two-step cooling preceding the start of the YD (Fig. 2). In the first step δDaq values start to decrease by 25‰ at 13,090±37 year BP (±1σ) and reach an isotopic minimum at 12,883±35 year BP. This δDaq decline coincides with a 27‰ rise in ΔδDterr-aq, peaking at 12,883±35 year BP, and a ∼2 °C decrease in summer temperatures (Fig. 2), suggesting substantially drier and colder summer conditions. After a brief recovery, a second step occurs. At 12,700±52 year BP, δDaq values decrease again by at least 34‰. The drop in δDaq values straddles the pollen–stratigraphic AL–YD transition, which is a regional marker for major environmental changes resulted from hemispheric-scale cooling27 (Fig. 2). This shift coincides with a 26‰ rise in ΔδDterr-aq and a ∼3 °C decrease in summer temperatures, indicating a further change towards drier and colder summer conditions.

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