Sea Ice Update. Marika Holland and David Bailey. National Center for Atmospheric Research. CESM Workshop. University of Toronto

Transcription

1 Sea Ice Update Marika Holland and David Bailey National Center for Atmospheric Research CESM Workshop University of Toronto November June NCAR is sponsored by the National Science Foundation

2 Where we were one year ago Run 79. NH Sea Ice Run 79 Ann Mean Thickness (Years 72 91) Run 36 8/2/2017 CESM Workshop Marika Holland 2 June 2016 mholland@ucar.edu

3 CESM2 Update Multiple issues have put us behind schedule (see Jean Francois Lamarque s talk yesterday) Test runs we will discuss are short (<100 years for PI controls) Only showing results from PI control runs We focus on aspects of the sea ice and heat budgets that seem to be robust across test runs Focus mostly on Arctic conditions Caveat that these are not the final CESM2 integrations and things are still subject to change

4 CESM2 Update Changes have been made to the land ice runoff outside of Greenland and Antarctica Heat is now being used from the atmosphere to melt water before it enters ocean No longer have excessive (~100m) thick ice in the Canadian Archipelago

5 NH Sea Ice Extent Obs Annual cycle of NH Extent Runs Typically have a smaller annual cycle Less ice in winter than More ice in summer than

6 Arctic Sea Ice Snow Thickness Summer (JAS) Mean Snow Thickness Snow Thickness

7 Arctic Sea Ice Snow Thickness hs Arctic Ocean Mean J F M A M J J A S O N D Snow thickness on Arctic Sea Ice Arctic Ocean Mean Runs Have thinner snow on sea ice throughout the year Have snow free summers unlike May now have a bit too little snow compared to observations

8 snow Arctic Ocean Mean Arctic Precipitation 0.08 Snowfall rate 0.07 in cm/day J F M A M J J A S O N D Rainfall rate in cm/day rain Arctic Ocean Mean Runs Less snowfall throughout the year More rainfall present throughout year Realistic?? J F M A M J J A S O N D As discussed in Light et al. (2015) excessive snow cover in summer is related to episodic summer snowfall events

9 JJA Incoming Surface SW Radiation Arctic Surface ISCCP Heat Budget Incoming SW minus ISCCP has excessive incoming SW Radiation in the Arctic

10 Incoming SW Radiation Averaged over Arctic Ocean Arctic Surface fswdn Heat Budget Incoming SW W m Runs Incoming SW Bias is largely alleviated 0 J F M A M J J A S O N D Diamonds show SHEBA data for a real world reference Associated with mixed phase clouds Increase in super cooled water within clouds, which is more realistic

11 Annual Incoming Surface LW Radiation Arctic Surface ISCCP Heat Budget Incoming LW minus ISCCP has too little incoming LW Radiation in the Arctic

12 Incoming LW Radiation Averaged over Arctic Ocean flwdn Arctic Surface Heat Budget 280 Incoming LW 260 W m Runs Incoming LW Bias is improved 160 J F M A M J J A S O N D Diamonds show SHEBA data for a real world reference Also associated with simulation of mixed phase clouds

13 fhocn_ai Arctic Ocean Mean J F M A M J J A S O N D fhocn_ai Arctic b.e20.b1850.f09_g17.pi_control.all.180-le minus Arctic Ice Ocean Heat Exchange CESM2 has Less ocean heat flux to ice in summer due to decreased incoming SW radiation More ocean heat flux to ice in winter Due to ocean transport May not be robust as ocean is still spinning up -6 J F M A M J J A S O N D

14 Antarctic Sea Ice Extent Annual cycle of SH Extent Obs Runs Typically have a smaller annual cycle Less ice all year compared to Captures min in Feb

15 Antarctic Sea Ice Thickness CESM2 Test Run Runs Improved thickness pattern in SH Thicker ice present in Weddell Sea

16 Summary While CESM2 is not yet completed, some robust features are present in polar regions Snow cover in Arctic sea ice reduced due to changing precipitation Radiative fluxes over sea ice are much improved Less SW and more LW Associated with cloud changes Antarctic sea ice extent is reduced (improved) and thickness pattern is improved

17 Questions?