Strength of forest-albedo feedback in mid-Holocene climate simulations

Abstract. Reconstructions of the mid-Holocene climate, 6000 years before present, suggest that spring temperatures were higher at high northern latitudes compared to the pre-industrial period. A positive feedback between expansion of forest and climate presumably contributed to this warming. In the presence of snow, forests have a lower albedo than grass land. Therefore, the expansion of forest likely favoured a warming in spring, counteracting the lower insolation at the mid-Holocene. We investigate the sensitivity of the vegetation-atmosphere interaction under mid-Holocene orbital forcing with respect to the strength of the forest-albedo feedback by using a comprehensive coupled atmosphere-vegetation model (ECHAM5/JSBACH). We perform two sets of model simulations: a first set of simulations with a relatively weak reduction of albedo of snow by forest; and a second set of simulations with a relatively strong reduction of the albedo of snow by forest. We show that the parameterisation of the albedo of snow leads to uncertainties in the temperature signal. Compared to the set with weak snow masking, the simulations with strong snow masking reveal a spring warming that is three times higher, by 0.34 °C north of 60° N. This warming is related to a forest expansion of only 13%.

[1]  Petoukhov,et al.  The influence of vegetation-atmosphere-ocean interaction on climate during the mid-holocene , 1998, Science.

[2]  R. Aravena,et al.  Holocene Treeline History and Climate Change Across Northern Eurasia , 2000, Quaternary Research.

[3]  A. Hall,et al.  Using the current seasonal cycle to constrain snow albedo feedback in future climate change , 2006 .

[4]  J. Otterman,et al.  Effects of Nontropical Forest Cover on Climate , 1984 .

[5]  Thomas Raddatz,et al.  Parameterization of snow-free land surface albedo as a function of vegetation phenology based on MODIS data and applied in climate modelling , 2009 .

[6]  P. Vidale,et al.  Land–atmosphere energy exchange in Arctic tundra and boreal forest: available data and feedbacks to climate , 2000, Global change biology.

[7]  J. Kutzbach,et al.  Coupled atmosphere-ocean-vegetation simulations for modern and mid-Holocene climates: role of extratropical vegetation cover feedbacks , 2005 .

[8]  W. Collins,et al.  Global climate projections , 2007 .

[9]  G. Liston,et al.  Changing snow and shrub conditions affect albedo with global implications , 2005 .

[10]  A. Hall,et al.  Improving predictions of summer climate change in the United States , 2008 .

[11]  K. Holmgren,et al.  Climate change between the mid and late Holocene in northern high latitudes - Part 1: Survey of temperature and precipitation proxy data , 2010 .

[12]  T. Fichefet,et al.  Climate evolution during the Holocene: a study with an Earth system model of intermediate complexity , 2002 .

[13]  Andreas Roesch,et al.  Assessment of Snow Cover and Surface Albedo in the ECHAM5 General Circulation Model , 2006 .

[14]  A. Hall,et al.  What Controls the Strength of Snow-Albedo Feedback? , 2007 .

[15]  N. Noblet,et al.  Quantifying the role of biosphere-atmosphere feedbacks in climate change: coupled model simulations for 6000 years BP and comparison with palaeodata for northern Eurasia and northern Africa , 1997 .

[16]  T. Fichefet,et al.  Results of Pmip2 Coupled Simulations of the Mid-holocene and Last Glacial Maximum – Part 2: Feedbacks with Emphasis on the Location of the Itcz and Mid-and High Latitudes Heat Budget , 2007 .

[17]  Permalink,et al.  Arctic and boreal ecosystems of western North America as components of the climate system , 2000, Global change biology.

[18]  Alan H. Strahler,et al.  How does snow impact the albedo of vegetated land surfaces as analyzed with MODIS data? , 2002 .

[19]  J. Kutzbach,et al.  Feedbacks between climate and boreal forests during the Holocene epoch , 1994, Nature.

[20]  M. D. Schwartz,et al.  Spring phenology : nature's experiment to detect the effect of Green-up on surface maximum temperatures , 1990 .

[21]  L. Harvey.  On the role of high latitude ice, snow, and vegetation feedbacks in the climatic response to external forcing changes , 1988 .

[22]  Roger A. Pielke,et al.  Land–atmosphere energy exchange in Arctic tundra and boreal forest: available data and feedbacks to climate , 2000, Global change biology.

[23]  M. Claussen,et al.  Climate variability‐induced uncertainty in mid‐Holocene atmosphere‐ocean‐vegetation feedbacks , 2009 .

[24]  M. Claussen.  Late Quaternary vegetation-climate feedbacks , 2009 .

[25]  K. Holmgren,et al.  Corrigendum to "Climate change between the mid and late Holocene in northern high latitudes – Part 1: Survey of temperature and precipitation proxy data" published in Clim. Past, 6, 591–608, 2010 , 2010 .

[26]  V. Brovkin,et al.  Separation of atmosphere‐ocean‐vegetation feedbacks and synergies for mid‐Holocene climate , 2009 .

[27]  R. Pielke,et al.  The boreal forest and the polar front , 1995 .

[28]  André Berger,et al.  Long-term variations of daily insolation and Quaternary climatic changes , 1978 .

[29]  Pascale Braconnot,et al.  Sensitivity of paleoclimate simulation results to season definitions , 1997 .

[30]  Ross D. Brown,et al.  Recent Northern Hemisphere snow cover extent trends and implications for the snow‐albedo feedback , 2007 .

[31]  Kelly Elder,et al.  An Evaluation of Forest Snow Process Simulations , 2009 .

[32]  C. Hewitt,et al.  Evaluation of coupled ocean–atmosphere simulations of the mid-Holocene using palaeovegetation data from the northern hemisphere extratropics , 2008 .

[33]  Alan K. Betts,et al.  Albedo over the boreal forest , 1997 .

[34]  Victor Brovkin,et al.  Global biogeophysical interactions between forest and climate , 2009 .

[35]  Jens Kattge,et al.  Will the tropical land biosphere dominate the climate–carbon cycle feedback during the twenty-first century? , 2007 .

[36]  Sandy P. Harrison,et al.  Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid‐Holocene, and present , 2003 .

[37]  A. Timmermann,et al.  On the definition of seasons in paleoclimate simulations with orbital forcing , 2008 .

[38]  P. Braconnot,et al.  Synergistic feedbacks between ocean and vegetation on mid- and high-latitude climates during the mid-Holocene , 2004 .

[39]  Terhikki Manninen,et al.  Simulation of the effect of snow covered forest floor on the total forest albedo , 2009 .

[40]  Pinhas Alpert,et al.  Factor Separation in Numerical Simulations. , 1993 .

[41]  F. Stuart Chapin,et al.  Surface energy exchanges along a tundra-forest transition and feedbacks to climate , 2005 .

[42]  J. Overpeck,et al.  The role of oceanic forcing in mid‐Holocene northern hemisphere climatic change , 1999 .

[43]  Xubin Zeng,et al.  A global 0.05° maximum albedo dataset of snow‐covered land based on MODIS observations , 2005 .

[44]  Steven Platnick,et al.  Northern Hemisphere five-year average (2000-2004) spectral albedos of surfaces in the presence of snow: Statistics computed from Terra MODIS land products , 2007 .

[45]  N. C. Strugnell,et al.  First operational BRDF, albedo nadir reflectance products from MODIS , 2002 .

[46]  K. Holmgren,et al.  Climate change between the mid and late Holocene in northern high latitudes - Part 2: Model-data comparisons , 2010 .