The effect of snow/sea ice type on the response of albedo and light penetration depth (&amp;lt;i&amp;gt;e&amp;lt;/i&amp;gt;-folding depth) to increasing black carbon

A A Marks,M D King

doi:10.5194/tc-8-1625-2014

Abstract

Abstract. The optical properties of snow/sea ice vary with age and by the processes they were formed, giving characteristic types of snow and sea ice. The response of albedo and light penetration depth (e-folding depth) to increasing mass ratio of black carbon is shown to depend on the snow and sea ice type and the thickness of the snow or sea ice. The response of albedo and e-folding depth of three different types of snow (cold polar snow, wind-packed snow and melting snow) and three sea ice (multi-year ice, first-year ice and melting sea ice) to increasing mass ratio of black carbon is calculated using a coupled atmosphere–snow/sea ice radiative-transfer model (TUV-snow), over the optical wavelengths of 300–800 nm. The snow and sea ice types are effectively defined by a scattering cross-section, density and asymmetry parameter. The relative change in albedo and e-folding depth of each of the three snow and three sea ice types with increasing mass ratio of black carbon is considered relative to a base case of 1 ng g−1 of black carbon. The relative response of each snow and sea ice type is intercompared to examine how different types of snow and sea ice respond relative to each other. The relative change in albedo of a melting snowpack is a factor of four more responsive to additions of black carbon compared to cold polar snow over a black carbon increase from 1 to 50 ng g−1, while the relative change in albedo of a melting sea ice is a factor of two more responsive to additions of black carbon compared to multi-year ice for the same increase in mass ratio of black carbon. The response of e-folding depth is effectively not dependent on snow/sea ice type. The albedo of sea ice is more responsive to increasing mass ratios of black carbon than snow.

Highlights

Black carbon, a component of soot formed by incomplete combustion, strongly absorbs solar radiation (e.g.Mitchell, 1957; Highwood and Kinnersley, 2006; Hansen and Nazarenko, 2004; Jacobson, 2001; Ramanathan and Carmichael, 2008; Bond et al, 2013)
The results section will report the response of the albedo of snow/sea ice to increasing black carbon as a function of the type of snow and sea ice and secondly the response of efolding depth to the same changes in black carbon mass ratio and snow or sea ice type
The change in albedo and e-folding depth is reported relative to an albedo and efolding depth calculated with a black carbon mass ratio of ng g−1

Summary

Introduction

A component of soot formed by incomplete combustion, strongly absorbs solar radiation (e.g.Mitchell, 1957; Highwood and Kinnersley, 2006; Hansen and Nazarenko, 2004; Jacobson, 2001; Ramanathan and Carmichael, 2008; Bond et al, 2013). Black carbon deposited onto snow and sea ice causes increased absorption of incident solar radiation, decreased surface albedo and exacerbated melting (e.g. Chýlek et al, 1983; Warren, 1984; Warren and Wiscombe, 1985; Clarke and Noone, 1985; Ledley and Thompson, 1986; Warren and Clarke, 1990; Light et al, 1998; Grenfell et al, 2002; Jacobson, 2004; Flanner et al, 2007; Doherty et al, 2010; Yasunari et al, 2011; Painter et al, 2012; Reay et al, 2012; France et al, 2012; Goldenson et al, 2012; Holland et al, 2012; Bond et al., 2013). There is still a large degree of uncertainty in the possible effects of black carbon in snow and sea ice – for example, the 2007

Methods

Results

Discussion

Conclusion