Is the ocean broken?

US rivers are changing from blue to yellow and green, satellite images show

• From 1984 and 2018, using photos from NASA and the USGS Landsat program ---
• Over half of rivers showed a dominant hue of yellow
• Over a third of rivers were mostly green
• Just 8% of rivers were mostly blue
• Rivers turn green with more algae, or when the water carries less sediments
• Rivers turn yellow when they carry more sediment
• Northern and Western rivers tended to become greener, whereas the eastern regions tend toward yellow rivers

The changing hues can be viewed in an interactive map

 

Change is bad.

-Will (Dragonfly)

 

The older I get the more my body agrees with you!

 

Quick, somebody, grab a sponge!

 

Oceanographers have an explanation for the Arctic's puzzling ocean turbulence

• In most oceans, eddies are observed at every depth and are strongest at the surface
• In the Arctic Ocean summers have typical eddies, but in the winter there are no eddies in the first 50 meters below the ice
• Winter ice acts as a frictional brake, slowing surface waters and preventing them from speeding into turbulent eddies
• But at depth the ocean's salty, denser layers act to insulate water from frictional effects, allowing eddies to swirl year-round
• As the Arctic warms up we expect an Arctic that is much more vigorously unstable, which has implications for the large-scale dynamics of the Arctic system

The paper was published in the Journal of Physical Oceanography

 

NEWS | APRIL 30, 2020
NASA Space Laser Missions Map 16 Years of Ice Sheet Loss


By Kate Ramsayer,
NASA’s Goddard Space Flight Center


The Kangerdlugssup (pictured) and Jakobshavn glaciers in Greenland have lost roughly 14 to 20 feet (4 to 6 meters) of elevation per year over the past 16 years. Credit: NASA/Jim Yungel
› Larger view

Using the most advanced Earth-observing laser instrument NASA has ever flown in space, scientists have made precise, detailed measurements of how the elevation of the Greenland and Antarctic ice sheets have changed over 16 years.

The results provide insights into how the polar ice sheets are changing, demonstrating definitively that small gains of ice in East Antarctica are dwarfed by massive losses in West Antarctica. The scientists found the net loss of ice from Antarctica, along with Greenland's shrinking ice sheet, has been responsible for 0.55 inches (14 millimeters) of sea level rise between 2003 and 2019 – slightly less than a third of the total amount of sea level rise observed in the world's ocean.

So, what's responsible for the other 2/3rds?

-Will (Dragonfly)

 

NASA-led Study Reveals the Causes of Sea Level Rise Since 1900

...The researchers found that estimates of global sea level variations based on tide-gauge observations had slightly overestimated global sea levels before the 1970s. (Located at coastal stations scattered around the globe, tide gauges are used to measure sea level height.) They also found that mountain glacier meltwater was adding more water to the oceans than previously realized but that the relative contribution of glaciers to sea level rise is slowly decreasing. And they discovered that glacier and Greenland ice sheet mass loss explain the increased rate of sea level rise before 1940.

In addition, the new study found that during the 1970s, when dam construction was at its peak, sea level rise slowed to a crawl. Dams create reservoirs that can impound freshwater that would normally flow straight into the sea.

"That was one of the biggest surprises for me," said lead researcher Thomas Frederikse, a postdoctoral fellow at JPL, referring to the peak in global dam projects at that time. "We impounded so much freshwater, humanity nearly brought sea level rise to a halt."

Since the 1990s, however, Greenland and Antarctic ice sheet mass loss and thermal expansion have accelerated sea level rise, while freshwater impoundment has decreased. As our climate continues to warm, the majority of this thermal energy is absorbed by the oceans, causing the volume of the water to expand. In fact, ice sheet melt and thermal expansion now account for about two-thirds of observed global mean sea level rise. Mountain glacier meltwater currently contributes another 20%, while declining freshwater water storage on land adds the remaining 10%....


This infographic shows the rise in sea levels since 1900. Pre-1940, glaciers and Greenland meltwater dominated the rise; dam projects slowed the rise in the 1970s. Now, ice sheet and glacier melt, plus thermal expansion, dominate the rise. Tide-gauge data shown in blue and satellite data in orange. Credit: NASA/JPL-Caltech

 

So...
Is this saying that if/when all the polar ice sheets melt, we won't see ~56m of sea level rise, but >168m of sea level rise?

Where is all that water now? And, why is there a water shortage in much of the World? I'm quite skeptical of the explanations and conclusions. You can dam a river, but once the reservoir fills, the same flow resumes to the sea.

-Will (Dragonfly)

 

Not sure about your numbers. Can you provide references or show your math?

How would sea level change if all glaciers melted? | USGS

There is still some uncertainty about the full volume of glaciers and ice caps on Earth, but if all of them were to melt, global sea level would rise approximately 70 meters (approximately 230 feet), flooding every coastal city on the planet.
​

NASA or NOAA may have more recent/accurate estimates?

Where is all of what water?

• Ice caps melt and flow to the ocean.
• Mountain glaciers melt and flow to the ocean.
• When dams are built there may be quite a bit of water stored in the surrounding area due to the raised water table.

There are multiple reasons why there are water shortages.

• More people need more water.
• Different precipitation patterns due to changing climate.
• Melted mountain glaciers mean less water released during hot summer months.
• Warmer temperatures may cause more evaporation from land.

Not necessarily. Dams that are built for irrigation divert water from areas of excess precipitation to land in arid areas. Irrigation greatly increases the surface area of the water in the arid area, resulting in much greater losses due to evaporation.

 

Earlier in this thread, I believe I remember a declaration that if the Polar Ice Sheets melted, it would raise sea level by approximately 56m. If I'm misremembering and it's 70m, all the more astounding. My math is based upon the NASA article that says sea level rise only gets a third of its change from polar ice sheets. That means 2/3rds comes from another source.

I can't argue with the specific numbers, 70m is fine with me, but that means there's still 140m to account for. You are telling me that mountain glaciers and river runoff, that isn't glacier feed, plus the material expansion of warming seawater accounts to twice the amount of water trapped in the poles.

Actually, it should account for well above twice the amount, since as the polar ice sheets melt, the feed rate to the oceans should start to fall off until it tapers out completely. Assuming the feed rate of the other sources doesn't change, that leaves a period when the oceans continue to rise after the polar ice sheets, from this other source(s) continues to add to sea level rise.

Water is not "lost" to evaporation.

A warming atmosphere holds more moisture, and it may be enough to deplete the world's drinking water supplies, but that would lead to sea level dropping, not rising.

I'm afraid I'm still not seeing the numbers "add up". But then, While I have a background in Math, I've never been very good at it.

-Will (Dragonfly)

 

If the arctic icesheet melts, it won't raise sea level a drop. It's floating ice and displaces water equall to it's weight. Melted, it only refills the hole in the water it formerly displaced.

If the antarctic ice sheet melted, there would be a new sea interior to Antarctica, as there is a subsea level deep depression in that land. Ice expands when freezing and shrinks when reverting to water. However. There might be some sea rise resulting if Antarctica totally melted, but that is extremely unlikely without a major pole shift which would be catastrophic anyway.

 

The 1/3 to 2/3 ratio is just what it is right now. This ratio will change over time.

The amount of runoff from mountain glaciers will diminish as they become smaller. I grew up in Colorado, and glaciers that I hiked on as a kid (Andrews glacier in Rocky Mtn Nat'l Park, and Arapaho glacier that supplies Boulder's drinking water) are much smaller now than they use to be. In the past I have posted how India and some of the South American countries are already facing irrigation water shortages because of a diminished glacial-runoff water supply.

On the other hand, the Greenland and Antarctic ice sheets are a long, long way from totally melting. Their contribution to sea level rise will greatly increase. IIRC, it will take 1,000 years for all of Antarctic ice to melt at expected warming rates.

My guess is that thermal expansion and polar ice cap melt will edge towards becoming 50:50 contributors.

I agree with you, water is not "lost," just redistributed -- and that is the problem.

We humans tend to use our resources to the max. For instance, we build our culverts and drainage ditches and bridges to accommodate an expected amount of rainfall. If, due to climate change, we start getting a lot more rain in a particular area, roads may get flooded more often and farmer's fields may not dry out in the spring when anticipated. On the other hand, if an area starts receiving significantly less rain... well, you get the point.

I don't think any extra amount of moisture in a warmer atmosphere is a major contributor to sea levels. If all the water in the atmosphere rained out it would cover the Earth by only one inch. The common rule of thumb is that the moisture holding capacity of saturated air doubles for every 20°F increase in temperature. So if Earth's average temperature increased by 5°F, maybe that would decrease sea level by ~1/4"?

<laugh>

 

In practical terms you are correct, but technically you are mistaken. Arctic sea ice is less salty than Arctic Ocean sea water. This partly due to the fresh water precipitation that falls on it, and partly due to salt slowly leaching out of the ice over time. Since fresh water ice is less dense than salt water ice, when it melts it will more than fill up its salt water "hole" (but not by a whole lot). In Antarctica the effect is more pronounced since a fair amount of "sea ice" is actually floating fresh water glacial ice.

"Might"? <laugh>

You've made a number of questionable assertions, but you "might" consider that the above-sea-level ice is going melt before the below-sea-level ice, and that melted ice would certainly raise sea levels many tens of meters.

 

"Since fresh water ice is less dense than salt water ice, when it melts it will more than fill up its salt water "hole" (but not by a whole lot). In Antarctica the effect is more pronounced since a fair amount of "sea ice" is actually floating fresh water glacial ice.?"

In all cases. Displacement is weight, not density. A steel ship displaces it's weight and so does a slab of Styrofoam. The weight of the freshwater or less salty ice will melt and fill its hole. Not over fill it. In truth, it spreads out on top and the hole is filled with seawater slowly as the ice melts. Fresh ice melt replaces the seawater that filled the hole. Level remains the same. It isn't a flash process..Any salt that leached out increased salt content and specific gravity of surrounding sea. The melting ice simply combines equilibrium once more.

MIGHT be some SEARISE if ALL ANTARCTICA MELTED! THAT COULD ONLY HAPPEN IF ANTAECTICA SWITCHED PLACES WITH THE TROPICS, BUT WE WOULD ALREADY BE DEAD FROM HUGE TIDAL WAVES WASHING OVER CONTINENTS.

 

No -- think about it.

We agree that one kg of salt water ice will displace the same amount of sea water as one kg of fresh water ice. But because the melt water from the fresh ice is less dense than the melt water from the salt ice, the fresh melt water occupies a larger volume than the salt melt water.

Consider a more extreme example. A kg of frozen mercury vs a kg of frozen water. Which one displaces the most water? The water, of course. In fact the mercury is unable to displace enough water to float itself. So the volume of the water plus mercury will be considerably less than the volume of water plus melted ice.

If you add a kg of salt water to an exact volume of water, the increase in volume will be less than if you add a kg of fresh water to the same exact volume of water.