Notes on the Sense of TimeNotes on the Sense of Time

Peter RhinesPeter RhinesSchool of OceanographySchool of Oceanography

Dept of Atmospheric SciencesDept of Atmospheric SciencesHonors ProgramHonors Program

University of WashingtonUniversity of Washington

time

Haug et alNature 2006

Deep timeDeep timeshowing theshowing thecooling of thecooling of theEarth since theEarth since theend of the end of the Creaceous period Creaceous period (the dinosaur era).(the dinosaur era).There was little or noThere was little or nosnow or ice on Earthsnow or ice on Earththen. Abruptly, about 2.5then. Abruptly, about 2.5million years ago,million years ago,the curve startsthe curve startsoscillating wildly:oscillating wildly:the beginning of thethe beginning of theice ages ice ages

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 southtip of Greenland, known as Cape Farewell. He came backwith the map at the right, having found a fjord we couldpossibly sail through. We did, so and saved several dayssteaming to our goal, the Labrador Sea. The fjord wasabout 100 km of narrow passage between tall cliffs of ancientmountains, 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 firstdeep ice cores were being drilled on the summit of Greenland.The iceberg likely calved off the Jakobshavn glacier in westGreenland. The strata, faintly visible, record climates back 120,000 years. Air bubbles in the ice accurately give us awhiff of ancient climates, showing the high correlation betweenEarth’s temperature and the amount of carbon dioxide and methane in the air

Wikipedia: ice ages

Vostok ice core, Antarctica. The ice ages currentlyare in a 100,000 year cycle. The Earth is almost alwayscooling down, interspersed with sudden warming events:ice ages end quickly.

Antarctica was covered by ice about 40M years ago, and today we can Antarctica was covered by ice about 40M years ago, and today we can observe its mass field with orbiting satellites (the twins known as observe its mass field with orbiting satellites (the twins known as GraceGrace).).90% of the worlds ice is here. Only in the past 3 or 4 years has it been possible 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 meltto measure the mass of the Earth’s ice. Were Greenland to meltit would raise sea-level by 7m on average, throughout the globe, and it would raise sea-level by 7m on average, throughout the globe, and Antarctica’sAntarctica’smelting would contribute another 61m. Sea-level currently seems to be rising melting would contribute another 61m. Sea-level currently seems to be rising abouabou4 cm per decade, with substantial contributions from both melting ice and 4 cm per decade, with substantial contributions from both melting ice and global warming ( leading to thermal expansion of sea water).global warming ( leading to thermal expansion of sea water).

Vogelherd horse carved 32,000 years ago from mammoth tusk. This, along Vogelherd horse carved 32,000 years ago from mammoth tusk. This, along with the cave paintings in France and Spain, represent the earliest discovered 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 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 must have been just north of the site of this art. Development of human intelligence may have occurredintelligence may have occurredat times of extreme climate and climate change.at times of extreme climate and climate change.

PacemakersPacemakers

ice ages (40,000 year, now 100,000 ice ages (40,000 year, now 100,000 year cycles)year cycles)

Earth/Sun orbit: precession, Earth/Sun orbit: precession, ellipticity…ellipticity…

Let’s start with the sunLet’s start with the sun

diameter: 1.38 million km diameter: 1.38 million km distance from Earth (mean): 149.6 million km (93 million miles)*distance from Earth (mean): 149.6 million km (93 million miles)*

tilt of Earth’s rotation axis relative to its orbit round the sun:tilt of Earth’s rotation axis relative to its orbit round the sun:

23.523.50 0

the orbit is an ellipse, but only about 2% different from a the orbit is an ellipse, but only about 2% different from a circle: the orbital eccentriciy**= 0.017circle: the orbital eccentriciy**= 0.017

rotation period: 23.9 hoursrotation period: 23.9 hours length of day: 24 hourslength of day: 24 hours

On July 4 this year the Earth is farthest from the sun (aphelion); 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 fallingon 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 goeson Earth) in Jan than in July. As Northern Hemisphere goes, so goesclimate! climate!

The eccentricity shifts with 100,000 year period from 0.05 to nearly zero.The eccentricity shifts with 100,000 year period from 0.05 to nearly zero.perihelion shifts with 21,000 year periodperihelion shifts with 21,000 year periodobliquity (tilt of axis) shifts with 41,000 year period …..all these slight changes alter the obliquity (tilt of axis) shifts with 41,000 year period …..all these slight changes alter the

amount of sunshineamount of sunshineand its distribution at the Earth’s surface, somehow leading to ice ages….cycles of cold and and its distribution at the Earth’s surface, somehow leading to ice ages….cycles of cold and

warm climate.warm climate.

Averaged over the globe, sunlight falling on Earth in July (aphelion) is indeed about 7% less intense than it is in January 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 (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 4aphelion is about 400 F (2.3 F (2.300 C) higher than it is at perihelion." Earth is actually warmer when we're farther from the Sun C) higher than it is at perihelion." Earth is actually warmer when we're farther from the Sun!!

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www.cwru.edu, http://science.nasa.gov/headlines/y2001/ast03jul_1.htm

*(these two numbers together tell us how big the disc of the *(these two numbers together tell us how big the disc of the sun appears in the sky….the relationship issun appears in the sky….the relationship is tan ½tan ½ΘΘ = ½ diameter/distance (see diagram above) = ½ diameter/distance (see diagram above) For small angles tanFor small angles tanΘΘ us approximately us approximately ΘΘ, measured in radians. , measured in radians. So, So, ΘΘ = 1.38/149.6 = 0.00922 radians or .00922 x 360/2 = 1.38/149.6 = 0.00922 radians or .00922 x 360/2ЛЛ degrees. This is 0.53 degrees….roughly ½ degree,almost the samedegrees. This is 0.53 degrees….roughly ½ degree,almost the same angular size as the moon, which is why we have such perfect angular size as the moon, which is why we have such perfect eclipses)eclipses)========================================================================================**the eccentricity of an ellipse is defined as the ratio √(1-b**the eccentricity of an ellipse is defined as the ratio √(1-b22/a/a22)) where where a is the a is the largest diameter (the major axis) and b is perpendicular to it, the largest diameter (the major axis) and b is perpendicular to it, the smallestsmallestdiameterdiameter

angle Θ

disc of thesun

Earth

This wood and canvas kayak is of northwest Greenland design, with highThis wood and canvas kayak is of northwest Greenland design, with highbow designed to cut through big waves. Over 6000 years of occupation of bow designed to cut through big waves. Over 6000 years of occupation of that land, the kayak design was optimized slowly, and is competitive with anythat land, the kayak design was optimized slowly, and is competitive with anymodern plastic kayak. The difference is, “there’s nothing in this boat thatmodern plastic kayak. The difference is, “there’s nothing in this boat thatyou couldn’t eat”. It has a small ecological footprint.you 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 hourspoised 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 framemade 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 Here the floating Arctic sea ice, which is very animated in response to winds,winds,and is flowing in response to ocean circulation, contrasts the and is flowing in response to ocean circulation, contrasts the pearlescent icepearlescent icemountain of Greenland. It is the only high topography of the far mountain of Greenland. It is the only high topography of the far North, and North, and extends one quarter of the way between Pole and Equator (2000 km). extends one quarter of the way between Pole and Equator (2000 km).

The breathing of the Earth: phytoplankton at sea and green The breathing of the Earth: phytoplankton at sea and green plants on land…animation of the seasonal waxing and waning plants on land…animation of the seasonal waxing and waning of plants coverof plants cover

American Golden Plover .. seasonal migration: energy and time. The plover American Golden Plover .. seasonal migration: energy and time. The plover comes to ANWR, the coastal plain of Alaska, to have its young in summer, comes to ANWR, the coastal plain of Alaska, to have its young in summer, then it doubles its bodythen it doubles its bodyweight for the flight over the ocean to South America, eating no food on the weight for the flight over the ocean to South America, eating no food on the journey. Its northward migration depends on stopovers at reliable wildlife journey. Its northward migration depends on stopovers at reliable wildlife preserves in the U.S. preserves in the U.S. In ANWR the numbers of plovers seems to be declining at about 8% per In ANWR the numbers of plovers seems to be declining at about 8% per year, thoughyear, thoughit is very difficult to count them.it is very difficult to count them.

see RichardBrown’s short description of Arctic spring inVoyage 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 Whaling by the Inupiat natives of Alaska’s north slope (image by Charles Wohlforth, author of by Charles Wohlforth, author of The Whale and the The Whale and the Supercomputer). Supercomputer). These bowhead whales weight about These bowhead whales weight about 100,000 lbs and may live in excess of 200 years. This says 100,000 lbs and may live in excess of 200 years. This says something about the stability of their environment.something about the stability of their environment.

Southern hemisphere and northern hemisphere circulations: weather Southern hemisphere and northern hemisphere circulations: weather introduces new time-scales into high latitude life. Left is south polar view, right introduces new time-scales into high latitude life. Left is south polar view, right is north polar view.is north polar view.There are natural cycles over 10 years and longer, as well as global warming There are natural cycles over 10 years and longer, as well as global warming relatedrelatedchange in weather patterns, temperature and rainfall.change in weather patterns, temperature and rainfall.(dynamic height at 1000 Hpa (colors: blue = low pressure cyclones, red=high (dynamic height at 1000 Hpa (colors: blue = low pressure cyclones, red=high pressure anticyclones), 300 Hpa, 30 Hpa 1993 (NH), 1996 (SH) winters, 100 pressure anticyclones), 300 Hpa, 30 Hpa 1993 (NH), 1996 (SH) winters, 100 days eachdays each

Andy Goldsworthy, Rivers and Tides

Roald Amundson finally Roald Amundson finally navigated the entire NW passage in navigated the entire NW passage in 1903-1906. Harald Sverdrup then 1903-1906. Harald Sverdrup then joined Amundson on the joined Amundson on the MaudMaud for for their 6 years in the western Arctic, their 6 years in the western Arctic, 1919-1925.1919-1925.

Accelerating polar melting (e.g. Abdalati Accelerating polar melting (e.g. Abdalati 2006):2006):

Sea-level rise, formerly dominated by Sea-level rise, formerly dominated by simple thermal expansion, is feeling increasing simple thermal expansion, is feeling increasing melt contribution. melt contribution.

Of the ~ 3 mm yrOf the ~ 3 mm yr-1-1 rise, fully 0.4 mm yr rise, fully 0.4 mm yr-1-1 came came from Antarctic melting and 0.25 mm yrfrom Antarctic melting and 0.25 mm yr-1-1 from from Greenland melting, 0.27 mm yrGreenland melting, 0.27 mm yr-1 -1 from Alaskan from Alaskan glaciersglaciers((± large error bars)± large error bars) in 2002-2005; alimeters, GRACE in 2002-2005; alimeters, GRACE gravity gravity satellitessatellites

Ice-sheet models did not have the rapid-Ice-sheet models did not have the rapid-response of bed lubrication to surface melting response of bed lubrication to surface melting and so this was and so this was a surprise.a surprise.