Limits...
On the nature of the sea ice albedo feedback in simple models.

Moon W, Wettlaufer JS - J Geophys Res Oceans (2014)

Bottom Line: It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions.Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback.Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.

View Article: PubMed Central - PubMed

Affiliation: Institute of Theoretical Geophysics, Department of Applied Mathematics and Theoretical Physics, University of Cambridge Cambridge, UK ; Yale University, New Haven Connecticut, USA.

ABSTRACT

We examine the nature of the ice-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea ice. The central issue examined is how the evolution of the ice area is treated when modeling a partial ice cover using a two-category-thickness scheme; thin sea ice and open water in one category and "thick" sea ice in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional ice cover and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions. Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.

No MeSH data available.


Related in: MedlinePlus

The three plots show two sets of solutions for the evolution of the dimensionless ice volume, ice area , and the mixed layer energy as a function of greenhouse gas forcing  (W m−2). The dash-dot lines (open diamonds) show the solutions of the equations above in which area evolution is complete (area evolution is incomplete). In both cases, red shows the end of the summer (late August) and blue the end of the winter (late March). The differences are discussed in the text in more detail, but we note here that a principal feature is that when area evolution is incomplete, substantially higher values of  are required before seasonal or perennial ice is lost.
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fig02: The three plots show two sets of solutions for the evolution of the dimensionless ice volume, ice area , and the mixed layer energy as a function of greenhouse gas forcing (W m−2). The dash-dot lines (open diamonds) show the solutions of the equations above in which area evolution is complete (area evolution is incomplete). In both cases, red shows the end of the summer (late August) and blue the end of the winter (late March). The differences are discussed in the text in more detail, but we note here that a principal feature is that when area evolution is incomplete, substantially higher values of are required before seasonal or perennial ice is lost.

Mentions: Finally, the persistent convergence and divergence of the wind field results in an observed net average annual export of v0 = 10% of the ice area. Thus, the ice dynamics are represented in such a model by requiring that , and a term is added to the area evolution equation (which accounts for volume export). Export is included in the results shown in Figure 2, but to avoid the clutter in the theoretical development, we omit the term in the equations that follow because it has no effect on the main points.


On the nature of the sea ice albedo feedback in simple models.

Moon W, Wettlaufer JS - J Geophys Res Oceans (2014)

The three plots show two sets of solutions for the evolution of the dimensionless ice volume, ice area , and the mixed layer energy as a function of greenhouse gas forcing  (W m−2). The dash-dot lines (open diamonds) show the solutions of the equations above in which area evolution is complete (area evolution is incomplete). In both cases, red shows the end of the summer (late August) and blue the end of the winter (late March). The differences are discussed in the text in more detail, but we note here that a principal feature is that when area evolution is incomplete, substantially higher values of  are required before seasonal or perennial ice is lost.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508964&req=5

fig02: The three plots show two sets of solutions for the evolution of the dimensionless ice volume, ice area , and the mixed layer energy as a function of greenhouse gas forcing (W m−2). The dash-dot lines (open diamonds) show the solutions of the equations above in which area evolution is complete (area evolution is incomplete). In both cases, red shows the end of the summer (late August) and blue the end of the winter (late March). The differences are discussed in the text in more detail, but we note here that a principal feature is that when area evolution is incomplete, substantially higher values of are required before seasonal or perennial ice is lost.
Mentions: Finally, the persistent convergence and divergence of the wind field results in an observed net average annual export of v0 = 10% of the ice area. Thus, the ice dynamics are represented in such a model by requiring that , and a term is added to the area evolution equation (which accounts for volume export). Export is included in the results shown in Figure 2, but to avoid the clutter in the theoretical development, we omit the term in the equations that follow because it has no effect on the main points.

Bottom Line: It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions.Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback.Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.

View Article: PubMed Central - PubMed

Affiliation: Institute of Theoretical Geophysics, Department of Applied Mathematics and Theoretical Physics, University of Cambridge Cambridge, UK ; Yale University, New Haven Connecticut, USA.

ABSTRACT

We examine the nature of the ice-albedo feedback in a long-standing approach used in the dynamic-thermodynamic modeling of sea ice. The central issue examined is how the evolution of the ice area is treated when modeling a partial ice cover using a two-category-thickness scheme; thin sea ice and open water in one category and "thick" sea ice in the second. The problem with the scheme is that the area evolution is handled in a manner that violates the basic rules of calculus, which leads to a neglected area evolution term that is equivalent to neglecting a leading-order latent heat flux. We demonstrate the consequences by constructing energy balance models with a fractional ice cover and studying them under the influence of increased radiative forcing. It is shown that the neglected flux is particularly important in a decaying ice cover approaching the transitions to seasonal or ice-free conditions. Clearly, a mishandling of the evolution of the ice area has leading-order effects on the ice-albedo feedback. Accordingly, it may be of considerable importance to reexamine the relevant climate model schemes and to begin the process of converting them to fully resolve the sea ice thickness distribution in a manner such as remapping, which does not in principle suffer from the pathology we describe.

No MeSH data available.


Related in: MedlinePlus