Multi-Column Ocean Grid (MCOG) Representation
For the Community Earth System Model
Marika Holland, Gokhan Danabasoglu and Bruce P. Briegleb
National Center for Atmospheric Research
Meibing Jin, Jennifer K. Hutchings and Igor V. Polyakov
International Arctic Reserarch Center
Robert W. Hallberg and Michael Winton
Geophysical Fluid Dynamics Laboratory
Overview
• CESM Sea Ice/Ocean Exchange
• MCOG Representation
• MCOG First Results
• Summary and Future Work
CESM Sea Ice/Ocean Exchange
n = 1, Ncat categories
m = 1, Nstp time steps
Sea Ice Component
cat
Am = ΣN
n=1 (anm )
cat
Fm = ΣN
n=1 (anm Fnm ) / Am
Coupler
N
A=
stp
(Am )/ Nstp
Σm=1
F =
stp
stp
(Am Fm )/ Nstp
(1 − Am )(F atm)m / Nstp + Σm=1
Σm=1
N
N
Grid Box Averaged Fluxes to Ocean Component
Focn = Fatm ∗ (1 − A) + Fice ∗ A
Frazil Ice in Ocean Component surface layer: δT, δS
MCOG Representation
Sea Ice Component
{anm , Fnm } n = 1, Ncat categories
m = 1, Nstp time steps
Coupler
N
stp
(anm ) / Nstp
an = Σm=1
cat
1 = ΣN
n=0 an
N
stp
(anm Fnm ) / an Nstp
Fn = Σm=1
N
stp
(1 − anm )F anm / (1 − A) Nstp
F0 = Σm=1
Category Fluxes to Ocean Component
an
nth category grid box ice f raction
Fn
nth category f lux
{n} (0, Ncat = 5 categories)
Frazil Ice contribution to Open Ocean (n = 0) buoyancy
Applying MCOG to KPP
cat
h = ΣN
n=0 an hn
boundary layer depth
cat
k = ΣN
n=0 an kn
vertical dif f usivity
cat
µ = ΣN
n=0 an µn
vertical viscosity
Schematic of MCOG
Open Ocean and Five Thickness Category Sea Ice
MCOG First Results
• CESM4 Release Code Base
• gx3 Ocean/Sea Ice with Normal Year Forcing
• Out-of-box 100 year Control Run
• MCOG parallel 100 year run
• Year 100 compared between MCOG and Control run
Summary of MCOG Impact
• Minimal
• IFRAC:
• hi:
Arctic < ±.005 and Antarctic mostly < ±.02
Typical regional values from −.01 m to +.02 m
• TEMP:
Polar values mostly less than ±.03 ◦ C
• SALT:
Polar values mostly less than ±.03 psu
• HBLT:
Typical regional values from −2.0 m to +1.0 m
• HBLT:
Systematic decrease −2 m to −10 m for polar coastlines
Boundary Layer Depth MCOG - CONTROL
ARCTIC Annual Mean
Boundary Layer Depth MCOG - CONTROL
ANTARCTIC Annual Mean
Boundary Layer Depth Annual Cycle: Northeast Greenland Coast
150
’mcog.dat’
’control.dat’
140
130
120
110
Bounday Layer Depth (m)
100
90
80
70
60
50
40
control 50.5 m
30
mcog
46.7 m
20
10
0
1
2
3
4
5
6
7
8
9
10
11
12
10
11
12
Month of year 100
150
’hblt0.dat’
140
’hblt1.dat’
130
’hblt2.dat’
120
’hblt3.dat’
Category Bounday Layer Depths (m)
110
’hblt4.dat’
100
’hblt5.dat’
90
80
70
60
50
40
30
20
mean 0
60.2 m
mean 1
49.0 m
mean 2
45.1 m
mean 3
44.1 m
mean 4
43.7 m
mean 5
43.1 m
1
3
10
0
2
4
5
6
7
8
Month of year 100
9
Boundary Layer Depth Annual Cycle: North of Greenland
90
’mcog.dat’
’control.dat’
80
70
Bounday Layer Depth (m)
60
50
40
mcog
40.2 m
control 37.9 m
30
20
10
0
1
2
3
4
5
6
7
8
9
10
11
12
10
11
12
Month of year 100
90
’hblt0.dat’
’hblt1.dat’
80
’hblt2.dat’
’hblt3.dat’
70
Category Bounday Layer Depths (m)
’hblt4.dat’
60
’hblt5.dat’
50
40
30
mean 0
42.6 m
mean 1
44.1 m
mean 2
41.4 m
mean 3
38.8 m
mean 4
36.5 m
mean 5
32.5 m
1
3
20
10
0
2
4
5
6
7
8
Month of year 100
9
Summary
• Deeper boundary layer depths in open ocean than sea ice
• Small decreases in polar coastal regions, 2 − 5 m
• Deepening/shallowing mostly in winter
• Very small changes in sea ice thickness and concentration
• Minimal impact on ocean T,S
• Overall, MCOG impact on mean state small
Future Work
• Fully coupled MCOG; more response?
• Simplified representation? Alternate parameterization?
• Combine with Ecosystem Model. How?
Category Fields for Northeast Greenland Coast, February
Field
0
1
2
3
4
5
.05
.39
-.079
.16
-.079
.26
-.079
.07
-.079
.07
-.079
-1.2E-02
3.4E-06
-1.6E-06
-3.9E-04
-1.9E-06
1.2E-06
-2.9E-07
-7.3E-05
-1.9E-06
2.2E-07
-1.6E-07
-3.9E-05
-1.9E-06
1.2E-07
-1.0E-07
-2.4E-05
-1.9E-06
7.3E-08
-2.3E-08
-5.6E-06
-1.9E-06
1.5E-08
1.24
1.11
1.11
1.11
1.11
1.11
Ice Frac
Heat
Frazil
17.0
Salt
Fresh
STF(T)
STF(S)
Ustar
Ri = g ′ h / { (∆u2 + ∆v 2 ) + wm }
Sea Ice Fraction Annual Cycle: Northeast Greenland Coast
1
’ifrac0.dat’
’ifrac1.dat’
’ifrac2.dat’
’ifrac3.dat’
’ifrac4.dat’
’ifrac5.dat’
0.9
0.8
Category Sea Ice Fractions
0.7
0.6
mean 0
.20
mean 1
.34
mean 2
.14
mean 3
.17
mean 4
.07
mean 5
.08
1
3
0.5
0.4
0.3
0.2
0.1
0
2
4
5
6
7
Month of year 100
8
9
10
11
12
Boundary Layer Depth Annual Cycle: Antarctic Coast
100
’mcog.dat’
’control.dat’
90
80
control 39.9 m
Bounday Layer Depth (m)
70
mcog
35.6 m
60
50
40
30
20
10
0
1
2
3
4
5
6
7
8
9
10
11
12
11
12
Month of year 100
100
’hblt0.dat’
’hblt1.dat’
’hblt2.dat’
’hblt3.dat’
’hblt4.dat’
’hblt5.dat’
90
Category Bounday Layer Depths (m)
80
70
mean 0
39.5 m
mean 1
38.0 m
mean 2
33.4 m
mean 3
32.5 m
mean 4
32.2 m
mean 5
31.8 m
1
3
60
50
40
30
20
10
0
2
4
5
6
7
8
Month of year 100
9
10
CPT: Ocean Mixing Processes Associated with
High Spatial Heterogeneity in Sea Ice and
the Implications for Climate Models
Questions
1. How does MCOG work during the ice growth period?
2. How can MCOG be implemented in 3-D climate models?
3. How does MCOG influence physical and biogeochemical tracers
that have fluxes between ice and ocean?
4. How much can MCOG reduce uncertainties in climate models?
5. What is the importance of explicitly representing the high
ice/ocean flux spatial heterogeneity in climate processes
and feedbacks?