Winter sunset (photo by Paul Aniszewski from Shutterstock)
Today is the shortest day in the northern hemisphere, the official start of Winter. But don’t worry. Spring comes faster than any other season.
Because the Earth doesn’t move at a constant speed in its elliptical orbit, the seasons are different lengths. From a warmth perspective, the northern hemisphere is lucky. Our winter is the shortest season.
Winter, December-to-March: 89.0 days from winter solstice to vernal equinox
Spring, March-to-June: 92.8 days from vernal equinox to northern summer solstice
Summer, June-to-September: 93.6 days from the summer solstice to the autumnal equinox
Autumn, September-to-December: 89.8 days from the autumnal equinox to the winter solstice
So after the sun stands still at 4:28pm UTC (Universal Time) — 11:28am in Pittsburgh — it’ll start its journey northward.
Spring will be here soon.
p.s. Groundhog Day is halfway between the winter solstice and vernal equinox. It’s something to look forward to.
Overcast sky above a bare tree, Pittsburgh, PA, 11 Dec 2017 (photo by Kate St. John)
We’ve had a long run of overcast days that began on Sunday, December 10.
On Monday morning Pittsburgh looked gray outside my window.
Overcast sky in Pittsburgh, 11 Dec 2017, 8:15am (photo by Kate St. John)
On Tuesday it was so gloomy that a few street lights came on in Schenley Park at 11:30am.
Overcast sky in Pittsburgh, 12 Dec 2017, 11:30am (photo by Kate St. John)
On Wednesday we had a splash of sun in the morning, then overcast skies and snow. Here’s the sky above PPG Place downtown on Wednesday at 4:15pm. The rest of the week was partly overcast, too.
The sky above PPG Place on Fourth Avenue, 13 Dec 2017, 4:15pm (photo by Kate St. John)
This is not just one layer of clouds. It’s often one or two low layers of broken clouds overtopped by an overcast layer.
12 Dec 11:35am … BKN008 OVC039 = Broken clouds at 800 feet, Overcast at 3,900
13 Dec 4:16 pm … FEW014 OVC024 = Few clouds at 1,400 feet, Overcast at 2,400
16 Dec 7:00am … OVC041 = Overcast at 4,100
My husband tries to see the good in everything. He sees value in a rainy day (we need rain on a regular basis) so he wondered, “What’s the value of an overcast day? What good is it?”
Ummm… perhaps… You can’t get a sunburn when the clouds are this thick.
Though the ocean will never flood Pittsburgh, I’m still fascinated by the rising sea.
Back in October I wrote about sea level fingerprints, the pattern of tiny elevation changes in sea level caused by uneven gravitational forces around the globe. The highest ocean peaks are in the tropics, the deepest valleys are near melting glaciers. As the land loses mass (ice) its gravitational pull decreases and it stops hugging the ocean to its shore. The water has to go somewhere so it goes to the tropics.
This means that glacial melt affects sea level rise in two ways:
It adds water to the ocean that used to be sequestered on land and …
It alters the sea level fingerprint, lowering the ocean nearby and raising it far away.
If you do the complicated math, you can find out how individual melting glaciers will affect sea level at specific locations.
Last month, scientists at NASA Jet Propulsion Lab did just that when they published a paper in Science Advances and an online tool that illustrates how glaciers will affect 293 coastal cities.
Let’s take a look at Miami.
Almost half the sea level rise in Miami will be caused by glaciers (47.4% of total sea level rise) and almost half of that will be Greenland’s fault (20% of total sea level rise). That’s why Greenland is so red in the screenshot above.
The next highest glacial contributor in Miami will be Antarctica (12% of total sea level rise). In the screenshot below you can see that South American glaciers help, too.
In fact, the entire northern hemisphere is endangered by Antarctica’s melting ice because it’s so far away. Ironically the safest place to be is right next to a melting glacier. Sea level will go down at those sites.
(*) Pittsburgh’s Point is 711 feet above sea level. My immediate family lives 10 to 25 feet above sea level in Virginia and Florida.
(screenshots of glacial contribution to sea level rise in Miami from the online tool at NASA Jet Propulsion Lab. On the first screenshot I added a pink circle to highlight Miami. Click on the images to use the online tool.)
Damage from 5 Nov 2017 tornado in Williamsfield, Ohio (photo from National Weather Service, Cleveland)
13 November 2017
You know things are strange when there’s an outbreak of 15 tornadoes in Ohio and western Pennsylvania in November.
Just over a week ago, on Sunday November 5, 2017, a cold front passed over the southern Great Lakes and Ohio River Valley. Before the front arrived it was humid and around 70 degrees — as much as 17 degrees above normal — so the front’s leading edge spawned 15 tornadoes in Ohio and PA.
The National Weather Service in Cleveland mapped 14 of them in their region. I’ve added the EF-1 tornado in Calcutta, Ohio just west of Beaver County, PA reported by the National Weather Service in Pittsburgh. Yes, 15 tornadoes!
Map of Nov 5, 2017 Tornado Outbreak in Ohio and northwestern PA (map from National Weather Service Cleveland. I added 1 tornado reported by NWS Pittsburgh region in Columbiana County, Ohio)
The tornado in Williamsfield, Ashtabula County, Ohio was one of the strongest, an EF-2 with winds of 127 miles per hour. It cut a swath 7 miles long ending at the western shore of Pymatuning Lake. The damaged house shown above makes me glad I wasn’t there!
This [Calcutta, Ohio tornado] is the 14th confirmed tornado so far this year in our county warning area. On average, we see five tornadoes a year. This is the first November tornado since 2003 /14 years/ in New Philadelphia, Ohio. This is the 5th tornado in November for Columbiana county since 1950.
screenshot from Business Insider video, with markup
24 October 2017
What would Earth look like if all the ice melted? In April 2017 Business Insider published a video showing what our continents would look like if that happened.
American beech leaf, 17 October 2017 (photo by Kate St. John)
By now fall colors ought to be at their peak in southwestern Pennsylvania but that isn’t the case this year.
Above, an American beech leaf shows hints of green and yellow but is already mostly brown. The view below at Moraine State Park on Tuesday October 17 shows a landscape that’s still green or brown and leafless. There are no beautiful reds and yellows.
Lake Arthur at Moraine State Park, 17 October 2017 (photo by Kate St. John)
Emerald ash borer killed the trees that used to contribute yellow, orange and violet. This year September’s heat and drought suppressed the maples.
We’re still waiting for the oaks to change color but they will turn a muted red.
As ice sheets melt around the world, fresh water that used to be held on land is pouring into the ocean and sea level is rising. But it’s not rising uniformly. The transfer of mass (water) from land to sea causes changes in Earth’s gravity field. Mirroring the ripples in gravity, the water is high in some places and low in others like the ridges on a fingerprint.
The mysteries of gravity *
Gravity is a force of attraction. It works on everything and in both directions. The Earth’s mass pulls you toward it while your mass pulls Earth toward you. The bigger the mass, the stronger the object’s gravitational pull. Greenland with an ice sheet on top has more mass than Greenland without one, so as the ice melts Greenland’s gravitational pull goes down.
As Greenland’s gravity wanes it doesn’t hug the ocean to its shore like it used to. The water has to go somewhere so it rises in the tropics. The effect is tiny, measured in millimeters per year. The pattern is called a sea level fingerprint.
The pattern revealed
Many things contribute to sea level at any given point including the Moon’s gravitational pull (causing tides) and the wind (causing waves) so it took lots of data and some serious number crunching to reveal Earth’s gravitational fingerprint. The data came from the GRACE satellite project.
GRACE satellites have been circling the Earth since 2002, measuring the pull of gravity on the globe below. (Here’s how GRACE works.) Each orbit provides a snapshot. Years of data show the change in gravity over time. Most gravitational changes are due to the movement of water, especially groundwater.
Sea level fingerprints (patterns of variation in sea level rise) calculated from GRACE satellite observations, 2002-2014. The blue contour (1.8 millimeters per year) shows the average sea level rise if all the water added to the ocean were spread uniformly around Earth. Image credit: NASA/UCI
Notice that the ocean has receded the most near Greenland at the rate of -2.5 mm/year. That’s 32.5 mm or 1.28 inches in the 13 years that GRACE measured it. As NASA explains:
The loss of mass from land ice and from changes in land water storage increased global average sea level by about 0.07 inch (1.8 millimeters) per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica and 30 percent from mountain glaciers.
Click here to read more about the study and see an animated map of sea level changes 2002-2014.
Unfortunately some of the hardest hit places will be tiny Pacific islands and Florida.
* p.s. Gravity is so mysterious that I initially described it incorrectly. Thanks to Dr. Allen Janis, I’ve corrected the description. See his comment below.
In this video by Yale Climate Connections, Jørgen Peder Steffensen, an expert in ice core analysis from the Niels Bohr Institute, explains how the Earth can become hotter yet simultaneously plunge Europe into an ice age and North America into ice or drought. It’s a matter of distribution.
Here are some points that stunned me in the video:
In the last 1 million years there have been 10 ice ages, each lasting about 90,000 years.
In-between ice ages are interglacial periods of milder, more stable climate that last about 10,000 years. We’re in an interglacial period right now. It’s already 11,000 years old.
Ice ages are not uniformly cold. Far from it! Steffensen says, “Inside an ice age the climate is extremely unstable, and you have this sequence of abrupt climate changes [semi-cold to very cold] that happen basically from one year to the next.”
Earth can have an ice age in one place and be hot elsewhere. Ice cores indicate that when Greenland has an ice age, Antarctica is warm — and vice versa.
Earth’s current mild climate is due to a global distribution pattern of ocean currents and pressure systems that keep temperatures mild and rainfall moderate.
The global distribution pattern can change abruptly. We don’t know where the trigger is, though we do know our emissions add fuel to the fire.
As Steffensen says, “The climate does not play nice all the time,”
Whimbrel (photo by Arturo Mann from Wikimedia Commons) This bird is not Hope.
News from the Caribbean, especially Puerto Rico, is horrific now that two Category 5 hurricanes have passed through the islands in just two weeks. Homes, infrastructure and habitat are all destroyed. Our hearts and help go out to everyone affected by these storms.
Images of the widespread damage also have made me wonder: Did birds survive these hurricanes?
North American whimbrels (Numenius phaeopus) that breed in the tundra of northwest Canada make long migrations to their wintering grounds in the Caribbean and South America. To understand their migration The Center for Conservation Biology fitted a few of them with satellite transmitters when the birds made migration stopovers on Virginia’s eastern shore. One bird, nicknamed Hope, was tracked for three years beginning in 2009. Her transmitter was removed after it broke in 2012 but she still wears two colorful leg tags. Every year she returns in late August to St. Croix.
St. Thomas and St.John (purple pin markers) took a direct hit from Irma. Hope spends the fall and winter on St. Croix (blue pin) at Great Pond (yellow star). She was fortunate that Irma passed more than 45 miles north of her location. St. Thomas and St. John were so devastated by Irma that survivors were evacuated to Puerto Rico and St. Croix. (Click here to see a video of Hurricane Irma damage on the U.S. Virgin Islands, posted by the U.S. Navy.)
Then on the night of September 19 Hurricane Maria blew through the islands, passing only 10 miles south of St. Croix. Hurricane force winds scraped the island for 7.5 hours before slamming Puerto Rico. The southwestern corner of St. Croix was hardest hit.
As with Hurricane Irma it will take a while to find out what happened.
And I wonder: Did Hope make it through Maria, too?
