On Tue, 17 Dec 2002, William B Ward <[EMAIL PROTECTED]> wrote:
>On Tue, 17 Dec 2002 08:25:54 -0800 "Lawrence de Bivort" ><[EMAIL PROTECTED]> writes: >> >> >> > -----Original Message----- >> > From: [EMAIL PROTECTED] >> > [mailto:[EMAIL PROTECTED]]On Behalf Of William >> B Ward >> > Sent: Tuesday, December 17, 2002 4:12 AM >> > To: [EMAIL PROTECTED] >> > Subject: Re: Ice sheets, etc >> > >> > >> > Harry and Keith, >> > >> > A somewhat scarier scenario is that the warm currents that flow >> past >> > Europe from the south Atlantic exist because of the temperature >> > differential and a mere change in ambient water temperatures in >> the north >> > could cause those currents to stop. Europe is farther north than >> the US >> > and the result would be to drop temperatures in western Europe >> > significantly. >> > >> > Bill Ward >> > >> Good morning, >> >> Isn't the current pattern of the north atlantic (including the Gulf >> Stream-Azores current portions) the result of corriolis (sp?) >> forces, rather >> than temperature gradients? >> >> Lawry > >Lawry, > >You may be right. Physics is not my strong suit but I got this second >hand from a news article which could make it even more suspect. The link >below is not the source of the info but additional info on the rapidity >of the changes that are occurring. > >http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=50 >27 > >Bill It's both, actually. Coriolis forces cause north-south motions to rotate, so moving north from the equator gives you a clockwise spin (and ccw moving south), but the engine which drives the northward motion in the first place is temperature, and the resulting "conveyor belt" of cold water from the poles travelling to the equator along the sea bottom while warm water flows to the poles along the surface. All sorts of things can interfere with this, as not only is the temperature of the water important, but the salinity, as the mechanism is convective, ie it depends on the density of the water. Cold salt water at the poles sinks, drawing the warm surface water in from the south. If, for example, a large quantity of fresh water were to suddenly be dumped into the north atlantic, as happened toward the end of the last ice age when glacial Lake Agassiz broke through to the St Lawrence, the lower density could stop the cycle, and chill europe. (The high temperatures of the terminal pleistocene, which ended the last ice age, weren't deterred by this event, however, and the retreat of the glaciers continued. This may be because the conveyor was probably not running during the ice age anyway, or at least not in the configuration it has now.) -Pete Vincent (still trying to catch up from the weekend...)
