Warm Arctic, increased winter sea‐ice growth?

by Alek Petty (2018)

Info

Citation

Petty, A. A., Holland, M. M., Bailey, D. A., & Kurtz, N. T. (2018), Warm Arctic, increased winter sea‐ice growth?, Geophysical Research Letters, 45, doi:10.1029/2018GL079223

Abstract

We explore current variability and future projections of winter Arctic sea ice thickness and growth using data from climate models and satellite observations. Winter ice thickness in the Community Earth System Model's Large Ensemble (CESM‐LE) compare well against thickness estimates from the Pan‐Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) and CryoSat‐2, despite some significant regional differences ‐ e.g. a high thickness bias in CESM‐LE in the western Arctic. Differences across the available CryoSat‐2 thickness products hinder more robust validation efforts. We assess the importance of the negative conductive feedback of sea ice growth (thinner ice grows faster) by regressing October atmosphere/ice/ocean conditions against winter ice growth. Our regressions demonstrate the importance of a strong negative conductive feedback process in our current climate, that increases winter growth for thinner initial ice, but indicate that later in the 21st century this negative feedback is overwhelmed by variations in the fall atmosphere/ocean state.

Plain Language Summary

In this study we explore the thickness and growth of Arctic sea ice through winter using data from climate models and satellite observations. Winter Arctic sea ice thickness in a widely used set of climate model simulations compares well against thickness estimates produced from a climate model constrained by observations and sea ice thickness estimates derived from satellite observations, although important regional differences are found. Our analysis suggest an increase in the amount of Arctic sea ice grown in winter through the coming decades, partly due to the fact thinner ice grows faster than thicker, more insulated, ice. As the Arctic warms rapidly, the strong atmosphere and ocean forcing dominates over this feedback and is projected to promote declines in sea ice growth.

FAQs

Q. Why is Arctic winter sea-ice growth increasing?
A. We think this is currently due to the negative feedback of sea-ice growth - thinner ice is less insulated and grows faster than thicker ice. We have more thinner ice in the Arctic thanwe used to have so it can regrow much faster despite the fact the Arctic winter is warmer than it used to be. Eventually the strong warming of the Arctic is expected to overcome this effect, however.

Q. Does this mean Arctic sea ice isn't in decline then?
A. No, Arctic sea ice is still very much in decline across all seasons and is projected to continue its decline over the coming decades (as shown in Figure 2 of the paper). We're mainly talking about an increase in the seasonal change, not the seasonal means, in this paper.

Q. Does this mean we might see a recovery or slowdown in Arctic sea ice loss?
A. No, the strong overall declines outweigh the increased amounts of ice grown in winter.

Q. Why do we care about an increase in winter Arctic sea-ice growth?
A. It's important for a number of reasons, including its impact on upper ocean mixing (brine is released as sea ice forms, which sinks and drives ocean mixing). The state of the upper ocean controls the biogeochemical balance of the upper Arctic Ocean.

Q. What does this have to do with sea level rise?
A. Nothing, really (sea ice is already floating so has a minimal effect on sea level rise).

Q. What about Antarctic sea ice?
A. Good question!

Bibtex

@article{doi:10.1029/2018GL079223,
author = {Petty, Alek A. and Holland, Marika M. and Bailey, David A. and Kurtz, Nathan T.},
title = {Warm Arctic, increased winter sea-ice growth?},
journal = {Geophysical Research Letters},
volume = {0},
number = {ja},
pages = {},
keywords = {Arctic, sea ice, climate models, satellite observations},
doi = {10.1029/2018GL079223},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GL079223},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL079223},
abstract = {Abstract We explore current variability and future projections of winter Arctic sea ice thickness and growth using data from climate models and satellite observations. Winter ice thickness in the Community Earth System Model's Large Ensemble (CESM-LE) compare well against thickness estimates from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) and CryoSat-2, despite some significant regional differences - e.g. a high thickness bias in CESM-LE in the western Arctic. Differences across the available CryoSat-2 thickness products hinder more robust validation efforts. We assess the importance of the negative conductive feedback of sea ice growth (thinner ice grows faster) by regressing October atmosphere/ice/ocean conditions against winter ice growth. Our regressions demonstrate the importance of a strong negative conductive feedback process in our current climate, that increases winter growth for thinner initial ice, but indicate that later in the 21st century this negative feedback is overwhelmed by variations in the fall atmosphere/ocean state.}
}