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Advection of Wind Reason for Europe's Relatively Mild Temperatures, Not Ocean Currents

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  • Pat Neuman, Hydrologist self-only
    SUMMARY Is the transport of heat northward by the Gulf Stream and North Atlantic Drift, and its subsequent release into the midlatitude westerlies, the reason
    Message 1 of 1 , Mar 4, 2004
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      SUMMARY

      Is the transport of heat northward by the Gulf Stream and North Atlantic
      Drift, and its subsequent release into the midlatitude westerlies, the
      reason why Europe�s winters are so much milder than those of eastern
      North America and other places at the same latitude? Here, it is shown
      that the principal cause of this temperature difference is advection by
      the mean winds. South-westerlies bring warm maritime air into Europe and
      northwesterlies bring frigid continental air into north-eastern North
      America.

      Further, analysis of the ocean surface heat budget shows that the
      majority of the heat released during winter from the ocean to the
      atmosphere is accounted for by the seasonal release of heat previously
      absorbed and not by ocean heat-flux convergence. Therefore, the existence
      of the winter temperature contrast between western Europe and eastern
      North America does not require a dynamical ocean.

      Two experiments with an atmospheric general-circulation model coupled to
      an ocean mixed layer confirm this conclusion. The difference in winter
      temperatures across the North Atlantic, and the difference between
      western Europe and western North America, is essentially the same in
      these models whether or not the movement of heat by the ocean is
      accounted for. In an additional experiment with no mountains, the flow
      across the ocean is more zonal, western Europe is cooled, the trough east
      of the Rockies is weakened and the cold of north-eastern North America is
      ameliorated.

      In all experiments the west coast of Europe is warmer than the west coast
      of North America at the same latitude whether or not ocean heat transport
      is accounted for. In summary the deviations from zonal symmetry of winter
      temperatures in the northern hemisphere are fundamentally caused by the
      atmospheric circulation interacting with the oceanic mixed layer.

      In the current paper we demonstrate that transport of heat by the ocean
      has little in� uence on the contrast between the mild winters of western
      Europe south of 60�N
      and the harsh ones of eastern North America. North of 60�N the OHT
      accounts for
      about a quarter of the contrast by restricting winter sea-ice cover.

      The dominant cause of the contrast, at both latitudes, is atmospheric
      advection around the Icelandic Low and the simple maritime�continental
      climate distinction. The exact positioning and strength of the Icelandic
      Low is important to the climate contrast and is shown to be greatly
      influenced by the orographic forcing of the Rocky Mountains.

      Therefore, the difference in the winter climates arises fundamentally
      through
      atmospheric processes and the seasonal storage and release of heat by the
      ocean mixed layer. This is also all that is required to establish the
      difference in winter climates between the west coast of Europe and the
      west coast of North America at the same latitudes.

      KEYWORDS: European winters
      http://www.atmos.washington.edu/~david/Gulf.pdf

      --------- Forwarded message ----------
      From: mtneuman@...
      To: Paleontology_and_Climate@yahoogroups.com
      Date: Wed, 3 Mar 2004 22:27:15 -0600
      Subject: [P&C] Advection of Wind Reason for Europe's Relatively Mild
      Temperatures, Not Ocean Currents

      Is the Gulf Stream responsible for Europe�s mild winters?
      By R. SEAGER1�, D. S. BATTISTI2, J. YIN2, N. GORDON1, N. NAIK1, A. C.
      CLEMENT3 and M. A. CANE1
      1Lamont Doherty Earth Observatory of Columbia University, USA
      2University of Washington, USA
      3Rosenstiel School of Marine and Atmospheric Sciences, USA
      (Received 23 July 2001; revised 19 April 2002)

      THE WORLD IS IN CRISIS DUE TO GLOBAL WARMING!
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      Thank you for your comments to P&C. [Pat N.]

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