Should the eastern US be dreaming of a White Christmas?

Image courtesy of Flickr user “angela n.”, used under Creative Commons.

The latest ENSO (El Niño-Southern Oscillation) Diagnostic Discussion forecast has been published (PDF) by NCEP and NOAA’s Climate Prediction Center.

As they have in previous weeks, most models are predicting a moderate-to-weak El Niño emerging in late summer/early fall, and persisting through the end of the year.

The early September probabilistic forecast shows much the same:

The etymology of El Niño derives from the fact that the phenomenon was noticed by fisherman off the coast of Peru around Christmas (Dec. 25) time. El Niño (“the Child”) refers to the infant Jesus. Wintertime El Niños are nothing new.

Meanwhile, you’ve probably been reading about the Arctic sea ice’s precipitous, newly record-breaking, and anthropogenically-driven (Notz and Marotzke, 2012; Day et al., 2012) decline:

Although some may “tut-tut” at the phrasing, you’re forgiven for noticing that it appears to be experiencing a “death spiral” of sorts:

What does sea ice have to do with an El Niño this winter? To answer that, it’s probably worth mentioning that sea ice appears to play a role in the phase of two other circulations, the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO). Although sometimes the AO and NAO are depicted as being interchangeable, they are distinct but related phenomena (Ambaum et al., 2001).

Recently,  increased attention has been given to the possible consequences of declining sea ice on high latitude NH  atmospheric circulation. A decline in autumn (and summer) sea ice (and ensuing changes in atmospheric circulation) has been linked to negative AO-like conditions  similar to but distinct from traditional negative AO excursions, and an increase in wintertime blocking (Liu et al., 2012; Francis and Varvus, 2012). These conditions appear to be partially responsible for negative temperature anomalies and increased water vapor in the high latitude NH and thus may have contributed to recent winter severity.

The decline of summer Arctic sea ice appears to be increasing the odds of delayed, negative NAO conditions in the autumn and winter (Bader et al., 2012). Additionally, one of the two drivers of daily wintertime NAO negative skewness, the sub-polar jet, appears to be at least partially driven by anthropogenic forcing (Woolings et al., 2010).

When negative AO and NAO conditions team up with a moderate to weak El Niño, the result can be a great deal of snow across much of the eastern US. This phenomenon occurred in the winter of 2009-2010, popularly referred to as “Snowmageddon“.

In the southeast, the combination of El Niño and the negative NAO altered typical storm tracks southward and increased precipitation contributed to the extreme snowfall, while the negative NAO’s influence on cold temperatures provided snowy conditions to more northern areas of the east coast (Seager et al., 2010).

So we have a moderate El Niño likely for this winter, and the continuing decline in Arctic sea ice may be loading the die towards negative AO/NAO (like) conditions. If such conditions reoccur, the eastern US might see a repeat of the winter wonderland (or miserable frozen hellscape, depending on your perspective) of 2009-2010.

Why bring this up, other than the fact that some readers live on the US east coast (and sledding is awesome)? Recall some recent instances of heavy Atlantic snowfall. The propaganda machine went into overdrive:

Image courtesy of Media Matters

The record-breaking mid-summer heat seen in the US, the 2010 Moscow heat wave and fires, the loss of Arctic sea ice, August being the 330th consecutive month of global temperatures above the 20th century average (and on and on), are a bit of an inconvenient truth for those in denial about the reality of anthropogenic warming. Counter-messaging is desperately needed. A snowy winter in cities like DC, Boston, and New York would (I wager) prove an irresistible temptation.

So while not a firm prediction, please consider this a “heads up”.

We shouldn’t be surprised to see snow- possibly even a large amount of snow- this winter across much of the US east coast. And if we do, it certainly does not call into question the scientific reality of anthropogenic global warming or our understanding of the climate system. On the contrary, if ENSO and NAO/AO team up to provide some wintertime excitement, that’s just the climate system behaving as we expect it to.

References

  • Ambaum, M. H. P., B. J. Hoskins, and D. B. Stephenson (2001), Arctic Oscillation or North Atlantic Oscillation?, Journal of Climate, 14(16), 3495–3507, doi:10.1175/1520-0442(2001)014<3495:AOONAO>2.0.CO;2.
  • Bader, J., M. D. S. Mesquita, K. I. Hodges, N. Keenlyside, S. Østerhus, and M. Miles (2011), A review on Northern Hemisphere sea-ice, storminess and the North Atlantic Oscillation: Observations and projected changes, Atmospheric Research, 101(4), 809–834, doi:10.1016/j.atmosres.2011.04.007.
  • CPC/NCEP (2012), El Niño/Southern Oscillation (ENSO) Diagnostic Discussion, URL: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf, retrieved 9/6/12.
  • Day, J. J., J. C. Hargreaves, J. D. Annan, and A. Abe-Ouchi (2012), Sources of multi-decadal variability in Arctic sea ice extent, Environmental Research Letters, 7(3), 034011, doi:10.1088/1748-9326/7/3/034011.
  • Francis, J. A., and S. J. Vavrus (2012), Evidence linking Arctic amplification to extreme weather in mid-latitudes, Geophys. Res. Lett., 39(6), L06801, doi:10.1029/2012GL051000.
  • Liu, J., J. A. Curry, H. Wang, M. Song, and R. M. Horton (2012), Impact of declining Arctic sea ice on winter snowfall, PNAS, 109(11), 4074–4079, doi:10.1073/pnas.1114910109.
  • Notz, D., and J. Marotzke (2012), Observations reveal external driver for Arctic sea-ice retreat, Geophys. Res. Lett., 39(8), L08502, doi:10.1029/2012GL051094.
  • Seager, R., Y. Kushnir, J. Nakamura, M. Ting, and N. Naik (2010), Northern Hemisphere winter snow anomalies: ENSO, NAO and the winter of 2009/10, Geophys. Res. Lett., 37(14), L14703, doi:10.1029/2010GL043830.
  • Woollings, T., A. Hannachi, B. Hoskins, and A. Turner (2010), A Regime View of the North Atlantic Oscillation and Its Response to Anthropogenic Forcing, Journal of Climate, 23(6), 1291–1307, doi:10.1175/2009JCLI3087.1.
About these ads

One response to “Should the eastern US be dreaming of a White Christmas?

  1. Pingback: Arctic Ice Is Disappearing and Our Weather Will Never Be The Same - Dan's Wild Wild Science Journal - AGU Blogosphere

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s