Friday, August 8, 2014

New paper finds hydroclimate of N. America & Asia linked to solar forcing & ENSO

A paper published today in the Journal of Climate reconstructs the hydroclimates of North America and the portions of Asia affected by monsoons over the past 600 years, and their connections to natural solar variability and the El Nino Southern Oscillation [ENSO]. 

The authors find connections ("teleconnections") between the hydrological changes in the two regions strengthen during periods of high solar forcing and weaken during periods of low solar forcing. Solar forcing changes can result from changes in solar activity, insolation, and cloud cover/albedo. 

Parsing the abstract for readability, the authors find:
This teleconnection [between N. America & Asia] is strengthened in periods of increased solar forcing and high temperature, which is associated with intensified ENSO variability.
This teleconnection [between N. America & Asia] is (weakened) in periods of (decreased) solar forcing and  (low) temperature, which is associated with (weakened) ENSO variability.
This would suggest that increased solar forcing increases ENSO variability & temperatures, and also strengthens teleconnections between the hydroclimates of North America and Asia, and vice-versa. Thus, this could potentially be another solar amplification mechanism by which small changes in solar activity have large-scale effects upon global climate. 

Covarying hydroclimate patterns between Monsoonal Asia and North America over the past 600 years

Keyan Fang,* Deliang Chen,2 Jinbao Li,3 and Heikki Seppä1
1 Department of Geosciences and Geography, PO Box 64, 00014 University of Helsinki, Helsinki, Finland
2 Department of Earth Sciences, University of Gothenburg, Box 460 S-405 30, Gothenburg, Sweden
3 Department of Geography, University of Hong Kong, Hong Kong

Proxy data with large spatial coverage spanning to the pre-industrial era provide not only invaluable material to investigate hydroclimate changes in different regions, but also enable studies on temporal changes in the teleconnections between these regions. Applying the Singular Value Decomposition (SVD) method to the tree-ring based field reconstructions of the Palmer drought severity index (PDSI) over the Monsoonal Asia (MA) and North America (NA) from 1404-2005, the dominant covarying pattern between the two regions is identified. This pattern is represented by the teleconnection between the dipole pattern of Southern–Northern latitudinal MA and the dipole of Southwest NA (SWNA)–Northwest NA (NWNA), which accounts for 59.6% of the total covariance. It is dominated by an anti-phase Low MA and SWNA teleconnection, driven by the El Niño-Southern Oscillation (ENSO), and is most significant at interannual timescale. This teleconnection is strengthened (weakened) in periods of increased (decreased) solar forcing and high (low) temperature, which is associated with intensified (weakened) ENSO variability. Additional forcing by the SST anomalies in Indian and western Pacific Oceans appears to be important too.

1 comment:

  1. High solar activity skews ENSO in favour of El Nino warming relative to La Nina cooling whereas low solar activity does the opposite.

    This describes how: