The west of England is milder and wetter, than the east, because the west is closer to the Atlantic and the east is nearer to the continent. A similar pattern repeats over North America, from west to east.
Not very similar, though:
https://nelson.wisc.edu/sage/data-and-models/atlas/maps/avgwintemp/atl_avgwintemp.jpg
The basic pattern of warmer in the west and colder in the east prevails over north America and Eurasia. The main difference is the mild temperatures extend further west into Europe, than they do into North America. There are a few reasons for this. Europe is a peninsula, with inland seas, America has the Rocky Mountains, which block the prevailing mild westerlies, so they don't get so far inland. The Rockies also send the jet stream on a north-west, to south-east trajectory, which results in the generation of intense low pressure systems and an increase in strength, as it hits the Atlantic, on eastern seaboard. This intense jet stream powers across the Atlantic, delivering mild air into Europe.
I do not know what is the main driver, but I definitely would not claim the Gulf Stream is irrelevant. (Note, neither did Zero999; they just said it is not the main driver.) The average winter temperature difference between Nunavut, Canada; Southern Greenland; and Iceland, breaks the "east-west part of continent dictates it" assertion, as they are all surrounded by ocean.
They're surrounded by cold ocean and are downwind of the frozen Arctic ocean and continent. Greenland has a mountainous interior and cold air sinking and flowing to the exterior makes it extremely cold. The Russian Far East is also very cold, despite being a peninsular.
The main reason I am wary of any simple explanations, is that Medieval Warm Period occurred, between c. 950 and 1100 Common Era. During this time, Vikings in (the southernmost tip of) Greenland had cattle, sheep, and goats, and only a quarter of their diet was seafood. By 1300, three quarters of their diet came from seal hunting, as livestock just couldn't handle the harsh winters. We do not know why it occurred: all we know is correlation, and can only guess (and try to simulate to ascertain) the causation.
I agree. I don't like simple explanations, which is why it makes no sense when people say Europe is mild because of the Gulf Stream. The reality is much more complex than that. Ocean currents play a role, but only a small part.
I grew up in Finland, north of the arctic circle (so about 6° further north), and for example potatoes, carrots, rutabaga, and onions grow just fine even at 330m above sea level there. (At the bottom of a couple of fell lakes, well above the treeline, there are still rather large tree trunks from the Medieval Warm Period, too.) So, it is not a small difference in winter temperatures; it is a clear difference that affects the entire biome.
The exact circulation patterns in the North Atlantic are rather interesting,
https://upload.wikimedia.org/wikipedia/commons/1/1e/North_Atlantic_currents.svg
Yes, interesting how the North Atlantic current misses all but most Northern Europe. The cold currents around Greenland and Eastern Canada help to push the July 10°C isotherm further south, although that's not he only reason.
Finally, comparing to the 10°C July mean isotherm (red line),
we can see that the summer mean temperature differs quite a bit from the winter mean temperatures in eastern Siberia and Alaska. This supports the reasoning for continental effect on the climate (continental winters being colder, summers hotter). However, the way Bering Sea summers are much colder than say Iceland clearly undermines that reasoning. In other words, simple theories based only on the polar jet stream, or only on the Gulf Stream, are doomed to fail even a cursory examination.
The pattern of colder on the east coasts fits the summer pattern quite well though:the Labrador Sea is pretty cold in summer.
The atmospheric circulation patterns for January and July are very revealing. Note how the high and low pressure areas are influenced by the landmasses? In the northern hemisphere wind blows clockwise around high pressure and anti-clockwise around low pressure.
In the northern winter, the strong Icelandic (polar) low, Bermuda (also often called the Azores high in Europe) (subtropical) and Siberian high help to push south-westerly winds over Eurasia. Areas to the east of the large landmasses experience a much colder climate because the polar lows deliver northerly winds. In North America, the pressure pattern is similar, but not exactly the same, which accounts for the differences in temperatures.
In summer the areas of high pressure in the subtropics move northwards and the polar lows weaken, giving more settled weather. Areas of low pressure sit in the middle of the continents, bringing about the monsoons.
Also note that there's very little land in the mid-latitudes in the southern hemisphere, so there's less blocking and the wind direction is just flat westerly.
Here's the site I got the charts from. It has a lot more information about the global atmospheric circulation pattern.
https://slideplayer.com/slide/677125/It's been disproven a long time ago that the Gulf Stream is the main driver for mild European winters. The west of England is milder and wetter, than the east, because the west is closer to the Atlantic and the east is nearer to the continent. A similar pattern repeats over North America, from west to east.
Yes, it's the jet stream which governs our weather. It's true it's affected by sea surface temperatures, but the correlation isn't direct. A warm North Atlantic doesn't necessarily mean milder winters for Europe. The temperature of the North Pacific, has a greater impact.
Links to sea surfaces temperature anomalies, at the end of Novembers 2010 and 2015, which preceded the coldest and mildest Decembers ever recorded in the UK. The Atlantic was much warmer at the end of 2010, than 2015. The difference was the Pacific was much colder in 2010, especially the north.
https://www.ospo.noaa.gov/data/sst/anomaly/2010/anomnight.11.29.2010.gif
https://www.ospo.noaa.gov/data/sst/anomaly/2015/anomnight.11.30.2015.gif
Of course there are many other factors. The weather has changed from cold in the first half of February, to near record breaking warm this week, because the jet stream has moved northwards, due to the North Atlantic oscillation flipping to the positive phase and now the wind is now coming from the Azores, rather than Svalbard. The sea surface temperatures haven't changed much and Gulf Stream didn't go way when it was cold and return now it's milder.
NOAA seems quite convinced of the importance of the Gulf Stream: https://scijinks.gov/gulf-stream/
And you can't really decouple the two: http://www.actforlibraries.org/jet-stream-gulf-stream-polar-shifts-and-climate-changes/
On the other hand, there's a lot of new evidence to show the Gulf Stream doesn't have as much effect, as previously thought.
https://www.google.com/search?client=firefox-b-d&q=gulf+stream+mythI agree it's impossible to decouple the two, but noting the above about how the land & sea interface, govern the global air circulation patten, suggests it's not so important. I agree that if the Gulf stream changed, it would affect the European climate, I very much doubt it would plunge us into the freezer, as many scaremongers say. The land and sea won't move that much, so the basic atmospheric circulation pattern won't change drastically.