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Notes on the Sense of Time. Peter Rhines School of Oceanography Dept of Atmospheric Sciences Honors Program University of Washington. Deep time showing the cooling of the Earth since the end of the Creaceous period (the dinosaur era). There was little or no snow or ice on Earth
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Notes on the Sense of Time Peter Rhines School of Oceanography Dept of Atmospheric Sciences Honors Program University of Washington
Deep time showing the cooling of the Earth since the end of the Creaceous period (the dinosaur era). There was little or no snow or ice on Earth then. Abruptly, about 2.5 million years ago, the curve starts oscillating wildly: the beginning of the ice ages time Haug et al Nature 2006
On my first voyage to Greenland, we approached from Iceland, and saw the coastal mountains covered in cloud. But then the clouds turned to ice. It was the ice cap, flowing slowly over the mountaintops to descend into the sea. Glaciers flow at rates of roughly 100m per year, yet they flow like rivers and produce trains of icebergs at sea. The Jakobshavn glacier at Illulissat in west Greenland has accelerated greatly in the past few years. You can see it flow! Emerson Hiller, the Captain of the Knorr, was an adventurer. As a joke I sent a request to him on the bridge showing the next day’s course…straight through the south tip of Greenland, known as Cape Farewell. He came back with the map at the right, having found a fjord we could possibly sail through. We did, so and saved several days steaming to our goal, the Labrador Sea. The fjord was about 100 km of narrow passage between tall cliffs of ancient mountains, with the ice sheet peering down from their tops, and small icebergs all round us.
R/V Knorr in Labrador Sea. At the time of this research cruise, the first deep ice cores were being drilled on the summit of Greenland. The iceberg likely calved off the Jakobshavn glacier in west Greenland. The strata, faintly visible, record climates back 120,000 years. Air bubbles in the ice accurately give us a whiff of ancient climates, showing the high correlation between Earth’s temperature and the amount of carbon dioxide and methane in the air
Vostok ice core, Antarctica. The ice ages currently are in a 100,000 year cycle. The Earth is almost always cooling down, interspersed with sudden warming events: ice ages end quickly. Wikipedia: ice ages
Antarctica was covered by ice about 40M years ago, and today we can observe its mass field with orbiting satellites (the twins known as Grace).90% of the worlds ice is here. Only in the past 3 or 4 years has it been possible to measure the mass of the Earth’s ice. Were Greenland to meltit would raise sea-level by 7m on average, throughout the globe, and Antarctica’smelting would contribute another 61m. Sea-level currently seems to be rising abou4 cm per decade, with substantial contributions from both melting ice and global warming ( leading to thermal expansion of sea water).
Vogelherd horse carved 32,000 years ago from mammoth tusk. This, along with the cave paintings in France and Spain, represent the earliest discovered art works of humans. This was the peak of the last ice age, when glacial ice must have been just north of the site of this art. Development of human intelligence may have occurredat times of extreme climate and climate change.
Pacemakers ice ages (40,000 year, now 100,000 year cycles) Earth/Sun orbit: precession, ellipticity…
disc of the sun Earth angle Θ Let’s start with the sun diameter: 1.38 million km distance from Earth (mean): 149.6 million km (93 million miles)* tilt of Earth’s rotation axis relative to its orbit round the sun: 23.50 the orbit is an ellipse, but only about 2% different from a circle: the orbital eccentriciy**= 0.017 rotation period: 23.9 hours length of day: 24 hours On July 4 this year the Earth is farthest from the sun (aphelion); on Jan 4 it was closest (perihelion); about 7% more sunlight (rate of energy falling on Earth) in Jan than in July. As Northern Hemisphere goes, so goes climate! The eccentricity shifts with 100,000 year period from 0.05 to nearly zero. perihelion shifts with 21,000 year period obliquity (tilt of axis) shifts with 41,000 year period …..all these slight changes alter the amount of sunshine and its distribution at the Earth’s surface, somehow leading to ice ages….cycles of cold and warm climate. Averaged over the globe, sunlight falling on Earth in July (aphelion) is indeed about 7% less intense than it is in January (perihelion)." That's the good news. The bad news is it's still hot. "In fact," says Spencer, "the average temperature of Earth at aphelion is about 40 F (2.30 C) higher than it is at perihelion." Earth is actually warmer when we're farther from the Sun! ========================================================================================= www.cwru.edu, http://science.nasa.gov/headlines/y2001/ast03jul_1.htm *(these two numbers together tell us how big the disc of the sun appears in the sky….the relationship is tan ½Θ = ½ diameter/distance (see diagram above) For small angles tanΘ us approximately Θ, measured in radians. So, Θ = 1.38/149.6 = 0.00922 radians or .00922 x 360/2Л degrees. This is 0.53 degrees….roughly ½ degree,almost the same angular size as the moon, which is why we have such perfect eclipses) ============================================ **the eccentricity of an ellipse is defined as the ratio √(1-b2/a2) where a is the largest diameter (the major axis) and b is perpendicular to it, the smallest diameter
This wood and canvas kayak is of northwest Greenland design, with highbow designed to cut through big waves. Over 6000 years of occupation of that land, the kayak design was optimized slowly, and is competitive with anymodern plastic kayak. The difference is, “there’s nothing in this boat thatyou couldn’t eat”. It has a small ecological footprint. 6 people,6 kayaks,6 days
Hunting seals is a major occupation of the north Greenlander. In winter, with much frozen ocean, the hunter waits for hours poised with a spear, for the seal to appear at a small breathing hole in the ice. His kayak, and the women’s umiak, is covered in seal-skin, with a light, strong frame made of drift wood. It’s length is twice the span of his arms (twice his height) and its width is his hips plus his hands.
Here the floating Arctic sea ice, which is very animated in response to winds,and is flowing in response to ocean circulation, contrasts the pearlescent icemountain of Greenland. It is the only high topography of the far North, and extends one quarter of the way between Pole and Equator (2000 km).
The breathing of the Earth: phytoplankton at sea and green plants on land…animation of the seasonal waxing and waning of plants cover
American Golden Plover .. seasonal migration: energy and time. The plover comes to ANWR, the coastal plain of Alaska, to have its young in summer, then it doubles its bodyweight for the flight over the ocean to South America, eating no food on the journey. Its northward migration depends on stopovers at reliable wildlife preserves in the U.S. In ANWR the numbers of plovers seems to be declining at about 8% per year, thoughit is very difficult to count them.
see Richard Brown’s short description of Arctic spring in Voyage of the Iceberg
Large Cod taken in the Godthåbsfjord W Greenland in 1951. The food chain in the Arctic is among the most intensely productive in spring…it lights up, from single-cell plankton to fish, whales and birds.
Whaling by the Inupiat natives of Alaska’s north slope (image by Charles Wohlforth, author of The Whale and the Supercomputer). These bowhead whales weight about 100,000 lbs and may live in excess of 200 years. This says something about the stability of their environment.
Southern hemisphere and northern hemisphere circulations: weather introduces new time-scales into high latitude life. Left is south polar view, right is north polar view.There are natural cycles over 10 years and longer, as well as global warming relatedchange in weather patterns, temperature and rainfall.(dynamic height at 1000 Hpa (colors: blue = low pressure cyclones, red=high pressure anticyclones), 300 Hpa, 30 Hpa 1993 (NH), 1996 (SH) winters, 100 days each
Roald Amundson finally navigated the entire NW passage in 1903-1906. Harald Sverdrup then joined Amundson on the Maud for their 6 years in the western Arctic, 1919-1925.
Accelerating polar melting (e.g. Abdalati 2006): Sea-level rise, formerly dominated by simple thermal expansion, is feeling increasing melt contribution. Of the ~ 3 mm yr-1 rise, fully 0.4 mm yr-1 came from Antarctic melting and 0.25 mm yr-1 from Greenland melting, 0.27 mm yr-1 from Alaskan glaciers(± large error bars) in 2002-2005; alimeters, GRACE gravity satellitesIce-sheet models did not have the rapid-response of bed lubrication to surface melting and so this was a surprise.
