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Variability and trends in sea ice cover and�dense-water formation along the East Greenland Current

Marte Vrålstad

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Variability and trends in sea ice cover and�dense-water formation along the East Greenland Current

Marte Vrålstad

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EGC(C)

East Greenland

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EGC domain (Moore et al., 2022)

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ROVER: The retreat of the ice edge over the East Greenland Current enhances re-ventilation of Atlantic-origin Water��My thesis: Investigating the ROVER hypothesis using GLORYS12 reanalysis

Hypothesis

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How does the retreat of sea ice influence the properties and transformation of Atlantic-origin Water in the EGC?��Are there indications of re-ventilation of Atlantic-origin Water in the EGC?� - Where?

Research Questions

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Data

  • GLORYS12
    • Global eddy-resolving ocean and sea ice reanalysis
    • Horizontal resolution: 1/12°
    • Vertical Resolution: 50 levels
    • Monthly data 1993-2020

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  • EGC domain following Moore et al. (2022)

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  • Winter years
    • Winter 1994 🡪 Dec 1993 – Mar 1994

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Data

  • GLORYS12
    • Global eddy-resolving ocean and sea ice reanalysis
    • Horizontal resolution: 1/12°
    • Vertical Resolution: 50 levels
    • Monthly data 1993-2020

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  • EGC domain following Moore et al. (2022)

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  • Winter years
    • Winter 1994 🡪 Dec 1993 – Mar 1994

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Sea ice

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Sea ice

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Atlantic-origin Water in the EGC

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Atlantic-origin Water Definition

 

More precise definition?

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Seasonal Temperature Variation of Atlantic-Origin Water in the EGC

Regime shift?

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Stratification in the EGC

Possible for Atlantic-origin Water to reach the surface?

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Convection Resistance

  • Amount of buoyancy that must be removed in order

for the water column to mix down to a depth h with

subsequent uniform density .

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Mean: 215m

190m

166m

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- 50% ice concentration

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Conclusion

  • Sea ice is diminishing over the EGC🡪 most significant reduction in southern region
  • Signs for re-ventilation of Atlantic-origin Water:
    • Split temperature signal: Warming in the north, cooling in south.
    • Increased seasonal temperature signal: prominent in areas with significant sea ice reduction.
    • Weaker stratification: decreased stratification above the Atlantic-origin Water in the southern EGC.

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  • Limitations/improvements:
    • Refine definition of Atlantic-origin Water.
    • Not ideal EGC domain?

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Questions/feedback?

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References

  • Moore, G. W. K., K. Våge, I. A. Renfrew, and R. S. Pickart (2022), Sea-ice retreat suggests re-organization of water mass transformation in the nordic and barents seas, doi:10.1038/s41467-021-27641-6. 1, 3.1
  • Håvik, L., M. Almansi, K. Våge, and T. W. Haine (2019), Atlantic-origin overflow water in the east greenland current, Journal of Physical Oceanography, 49, 2255– 2269, doi:10.1175/JPO-D-18-0216.1. 1, 3.2

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Extra Slides

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EGC domain (Moore et al., 2022)

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Sea ice

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15% ice contours

50% ice contours

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Heat fluxes

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Heat fluxes

- 50% ice concentration

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Atlantic-origin Water

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Buoyancy frequency

- 50% ice concentration

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Surface density

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Surface density

- 50% ice concentration