Earth Gauge » Oceans

Climate Number: 217 miles

kraus — Wed, 25 Aug 2010 20:54:21 +0000

Along America’s East Coast, blue mussels (Mytilus edulis) have traditionally been an important food source for larger species. They are also commercially farmed and even help improve water quality by filtering out pollutants as they feed. As recently as 50 years ago, blue mussels could be found as far south as the waters around Cape Hatteras, N.C. Yet, these species – like all species – have a thermal limit, meaning that once water and air temperatures reach certain levels, the animals die. Air and water temperature increases over the past 50 years along the Mid-Atlantic coast have pushed blue mussel populations farther north. At low-tide, the mussels are exposed to the open air. Multiple exposures to air temperatures of 89.6 degrees or greater kill the mussels and these types of conditions are now more common than they were 60 years ago. As temperatures have warmed, the mussels have retreated north. Now, intertidal blue mussels are not found south of Lewes, Del., indicating a northward shift in the southernmost extent of their range by about 217 miles.

For comparison: 217 miles is also about the same distance (as the crow flies) between Syracuse, N.Y. and Philadelphia, Pa.; Detroit, Mich. and Cincinnati, Ohio; or Los Angeles and Monterey, Calif.

Seasons: Spring, Summer, Fall

Sources: Jones, SJ et al. “Rising environmental temperatures and biogeography: poleward range contraction of the blue mussel, Mytilus edulis L., in the western Atlantic.” Journal of Biogeography. Published Online 19 August 2010, DOI : 10.1111/j.1365-2699.2010.02386.x and Science Daily. “Too Hot to Handle: Impacts of Climate Change on Mussels.” 19 August 2010. Accessed Online 25 August 2010

Climate Trivia: Ocean Acidification

kraus — Fri, 06 Aug 2010 20:32:18 +0000

The oceans are currently absorbing about 22 million tons of carbon dioxide (CO2) each day and have absorbed an estimated 525 billion tons of CO2 over the last 200 years.

Trivia Question: As the oceans absorb more carbon dioxide, they become…

a. more basic (higher pH).
b. more acidic (lower pH).
c. richer in nutrients.
d. warmer.

The correct answer is b. As oceans take CO2 out of the atmosphere, the waters become more acidic. More acidic waters mean there are less carbonate molecules available to organisms that use calcium carbonate to build their bodies, such as coral, oysters and many of the tiny plankton that are at the base of the food chain. One indicator of how this acidification has affected ocean life is the thickness of foraminiferan shells, which are a type of plankton. Samples from the Southern Ocean around Antarctica indicate that foramineferan shells, which are harder to make when there are fewer carbonate molecules, are now one-third thinner than they were in pre-industrial times.

Seasons: Winter, Spring, Summer, Fall

Sources: Hoegh-Guldberg et al. “Coral Reefs Under Rapid Climate Change and Ocean Acidification.” Science 318 (2007): 1737 and “Oceans Becoming More Acidic, Potentially Threatening Marine Life.” Science Daily 23 February 2009. Accessed Online 25 February 2009 and Moy, AD et al. “Reduced calcification in modern Southern Ocean planktonic foraminifera.” Nature Geoscience 2 (2009): doi:10.1038/ngeo460.

Climate Number: 0.006 milligrams per cubic meter per year

kraus — Mon, 02 Aug 2010 15:00:58 +0000

Oceanic phytoplankton – microscopic organisms that use the sun’s energy to convert carbon and water into the sugars that make up their bodies – account for about half of the production of organic, or living, matter on Earth. These phytoplankton feed the zooplankton, which eventually feed the larger fishes that feed seabirds, marine mammals and humans. In short, all life in the oceans is fueled by phytoplankton. Also, because phytoplankton do account for so much of Earth’s living matter, they play a key role in carbon uptake and thus the composition of the atmosphere, affecting land-based life in the process. The rise in global sea surface temperatures over the last century has resulted in more stratified oceans. Strongly stratified oceans have warm and nutrient poor surface layers, with less cool and nutrient rich water delivered to surfaces from the depths. The phytoplankton, which grow near the surface where sunlight is available, now have fewer nutrients to work with than they did in the early 20th century when temperatures were cooler. How many phytoplankton there are in the water is measured by chlorophyll concentrations. Chlorophyll is the chemical that enables the phytoplankton to harness the sun’s energy for life. On average, each cubic meter of seawater contains 0.56 milligrams of chlorophyll. This concentration is declining at a rate of 0.006 milligrams per cubic meter per year.

For Comparison: The amount of chlorophyll in one cubic meter of sea water, 0.56 milligrams, is about the same mass as 10 grains of salt.

Seasons: Winter, Spring, Summer, Fall

Sources: Boyce, DG et al. “Global phytoplankton decline over teh past century.” Nature 466(2010): 591-596 and Science Daily “Marine Phytoplankton Declining: Striking Global Changes at the Base of the Marine Food Web Linked to Rising Ocean Temperatures.” 28 July 2010. Accessed Online 31 July 2010

Climate Number: 179 Cubic Miles

kraus — Mon, 26 Jul 2010 13:19:52 +0000

Many of Earth’s great ice masses, which collectively form the cryosphere, are floating on ocean surfaces. There are three main collections of floating ice: the Arctic sea ice, the Antarctic ice shelves and the Antarctic sea ice. All three components have seasonal fluctuations, with the Antarctic sea ice showing the most dramatic differences between winter and summer extents. The Antarctic ice shelves are the edges of the Antarctic continent’s ice sheets that extend out onto the oceans. Every year, in each hemisphere’s respective summer, large portions of the floating ice either melts or breaks off into chunks known as icebergs that float off into the open ocean before melting. In a world with a static climate, about the same amount of ice that melts every summer would refreeze the following winter. Between 1994 and 2004, however, there was on average about 179 cubic miles less floating ice each year, indicating an overall loss of ice and a warming of the oceans and atmosphere. While this loss of floating ice contributes only minimally to sea level rise, such losses may impact ocean salinity, heat distribution and mixing. These changes may in turn lead to changes in the ocean current system, which may have other ramifications for the climate system.

For Comparison: 179 cubic miles is about the same size as three million Great Pyramids of Giza.

Seasons: Winter, Spring, Summer, Fall

Source: Shepherd, A et al. “Recent loss of floating ice and the consequent sea level contribution.” Geophysical Research Letters 37 (2010): L13503.

Climate Number: 120 Meters (394 feet)

kraus — Mon, 19 Jul 2010 14:13:18 +0000

For about the past two million years, Earth’s climate system has been characterized by glacial cycles that last between 80,000 to 120,000 years. These cycles have long periods when the Earth cools and ice sheets build up to their maximums, followed by relatively short warming periods when the ice retreats and then “interglacial periods” like the climate we inhabit today. Glacial maximums are characterized by Northern Hemisphere ice sheets extending from the Arctic all the way down to the Ohio River and central Europe, low carbon dioxide (CO2) concentrations (about 180 parts per million) and sea levels about 120 meters lower than today. Sea levels were lower because the water that is in the oceans today was in ice back then. From 20,000 to 7,000 years ago, Earth “deglaciated” and by about 5,000 BCE all that was left of the Northern Hemisphere ice sheet was a small remnant on Canada’s Baffin Island. Carbon dioxide levels by that point had risen to about 280 parts per million – where they remained until the early 19th century – and sea-levels and coastlines were about where they are today.

For Comparison: Twenty-thousand (20,000) years ago, when sea levels were 120 meters lower than today, the Bering Strait was dry land that served as a bridge for the ancestors of today’s Native Americans, who crossed the strait on foot around 15,000 years ago and settled North America. Indochina (Vietnam, Thailand, Cambodia, Laos) was connected by land to the Indonesian Islands of Sumatra, Java and Borneo. Much of the Florida coastline today was hundreds of miles inland back then. The black line in the image below (Image Courtesy of Exploring the Submerged New World 2009 Expedition NOAA-OER) marks the location of the Florida coastline 20,000 years ago.

Seasons: Winter, Spring, Summer, Fall

Source: Denton, GH et al. “The Last Glacial Termination.” Science 328 (2010): 1652-1655.

Climate Trivia: Atlantic Hurricane Frequence and ENSO

kraus — Mon, 21 Jun 2010 14:42:52 +0000

Warm ocean surface temperatures in the North Atlantic provide the warm and moist air that fuels hurricanes, which develop out of random disturbances in the tropics that provide the spark for these storms. Warmer waters in the North Atlantic generally mean more fuel for the storms. But did you know that surface temperature conditions in the tropical Pacific Ocean also influence the Atlantic Hurricane season? The El Niño-Southern Oscillation (ENSO) is the periodic shifting of sea surface temperature distributions in the tropical Pacific. During El Niño phases, water temperatures in the eastern tropical Pacific off the coast of South America are warmer than normal. During La Niña phases, water temperatures there are cooler than normal. During ENSO neutral phases, the temperatures are somewhat in between.

Trivia Question: All other things being equal, during what phase of ENSO does the Atlantic Hurricane season tend to be most active?

a. El Niño
b. La Niña
c. Neutral

The correct answer is b. The amount of vertical wind shear over the ocean can make or break a hurricane season. Vertical wind shear is the change in the speed and direction of wind at different levels of the atmosphere. More vertical wind shear, or lots of variation in wind speed across different altitudes, suppresses hurricane activity. Less vertical wind shear, or more even wind patterns across different altitudes, promote hurricane development. La Niña phases work to reduce the amount of vertical wind shear over the North Atlantic, and thus La Niña years tend to be years with more active Atlantic hurricane seasons. La Niña conditions are now present in the tropical Pacific.

Seasons: Summer, Fall

Sources: Briggs, WM. “On the Changes in the Number and Intensity of North Atlantic Tropical Cyclones.” Journal of Climate 21 (2008): 1387-1402. Donnely, JP and Woodruff, JD. “Intense hurricane activity over the past 5,000 years controlled by El Niño and the West African monsoon.” Nature 447 (2007): 465-468.

Climate Number: 180 Square Miles

kraus — Mon, 07 Jun 2010 14:24:15 +0000

The coral reefs around the 3,700 square mile Florida Keys National Marine Sanctuary provide habitat for 5,500 species as well nursing, feeding and breeding grounds that support a 20 million pound per year fishery. Water temperatures in the sanctuary fluctuate annually between about 68 and 86 degrees Fahrenheit. These waters, which reach their annual peak during the summer months, are currently approaching 85 degrees. While coral polyps can only survive in warm waters, if waters become too warm (86-87 degrees Fahrenheit is considered the “danger zone” for these corals) coral polyps lose the algae that they depend on for food and begin to die. This phenomenon, known as “coral bleaching,” has become more common as Atlantic sea surface temperatures have warmed, which they have been doing since the 1870’s. During El Niño years, such as 1982-1983 and 1997-1998, conditions where water temperatures are particularly high for an especially long period of time are common. Florida Keys coral cover fell from about 11.7 percent before the bleaching events that happened during the El Niño years of 1997-1998 to about 6.7 percent in 2005. This means that 180 square miles of shallow waters that were full of colorful coral ecosystems in 1996 had little or no living coral in 2005.

For Comparison: You could fit close to six Manhattans into 180 square miles; 180 square miles is also about the same size as Miami and Atlanta combined.

Seasons: Summer

Sources: Causey, Billy: “The History of Massive Coral Bleaching and other Perturbations in the Florida Keys.” In Chapter 6 of Coral Reefs in the U.S. and the Carribean. U.S. Coral Reef Information Service: National Oceanic and Atmospheric Administration and Eakin, Mark. Testimony before the House Committee on Natural Resources. U.S. House of Representatitves,17 April 2007 and Hoegh-Guldberg et al. “Coral Reefs Under Rapid Climate Change and Ocean Acidification.” Science 318 (2007): 1737 and United States. National Oceanic and Atmospheric Administration. Florida Keys National Marine Sanctuary: Visitor Information. 28 April 2008. Accessed Online: 18 September 2008 < http://floridakeys.noaa.gov/visitor_information/welcome.html> United States. National Oceanographic and Atmospheric Administration. NOAA Coral Reef Initiative. 1997. Accessed Online 18 September 2008 Wilkinson, C., Souter, D. (2008). Status of Caribbean coral reefs after bleaching and hurricanes in 2005. Global Coral Reef Monitoring Network and Reef and Rainforest Research Centre, Townsville, 152 p.

Climate Trivia: Sea Level and Ice Melt

kraus — Mon, 24 May 2010 13:49:46 +0000

By most estimates, Earth’s sea level rose by 3.5 mm per year between 1993 and 2006. About one-seventh of this sea level rise can be attributed to ice melt on one island – two to three days worth of the summertime melt water from the island could supply the New York Metropolitan area’s water needs for a year!

Trivia Question: Which island is this?

a. Baffin Island
b. Hokkaido (Japan’s northernmost Island)
c. Hawaii’s Big Island
d. Greenland

The correct answer is d. Greenland’s ice sheet, the world’s second largest ice sheet behind the Antarctic ice sheet, has been losing more ice during the summer melt season than it gains during the cold season. For the past few decades, Greenland has been losing about 57 cubic miles of ice each year. For further comparison, this ice melt is about 14 times the annual flow of the Colorado River.

Seasons: Spring, Summer, Fall

Sources: Steffen, K. “Cryospheric Contributions to Sea-Level Rise and Variability.” United States Senate, Washington, DC. 3 May 2007. Accessed Online 21 May 2010

Climate Number: 10 X 10²² joules

kraus — Mon, 10 May 2010 14:59:08 +0000

There is more energy in the Earth’s climate today than there was in 1950. This increase in energy exists in warmer air temperatures, less ice, more extreme rainfall events, warmer land surfaces and warmer rivers and lakes. The vast majority of the cumulative energy gain, however, is in the oceans. The upper 2300 feet of ocean waters have gained 10 x 10²² joules worth of heat energy over the past 60 years. Water expands as it gets warmer and this increase in heat content accounts for about 60 percent of the four inches of sea level rise experienced over the same period; melting glaciers account for the other 40 percent.

For Comparison: The amount of heat absorbed by the oceans is about 10 times the amount of heat absorbed by the atmosphere; 10 x 10²² joules worth of energy is about 60 years worth of electrical energy for America.

Below: A few estimates of ocean heat content increases. Image Courtesy of United States: Environmental Protection Agency. “Climate Change Indicators in the United States.” 2010.

Seasons: Winter, Spring, Summer, Fall

Sources: United States: Environmental Protection Agency. “Climate Change Indicators in the United States.” 2010. Accessed Online and World Nuclear Association. “Nuclear Power in the World Today.” Accessed Online 28 February 2010

Climate Number: 5.8 million square miles

kraus — Mon, 10 May 2010 14:34:53 +0000

One of Earth’s most dramatic seasonal cycles is the waxing and waning of the sea ice that surrounds Antarctica, the driest, darkest and coldest continent. At its maximum extent at the end of the Southern Hemisphere winter in September, a 6.9 million square mile expanse of ice extends from Antarctica’s shores out into the Southern Ocean. This 6.9 million square mile collection of ice is larger than the solid continent itself, which covers an area of about 5.4 million square miles. By the end of the Southern Hemisphere summer, however, the sea ice has shrunk to about 1.1 million square miles, a difference of about 5.8 million square miles or a 630 percent decrease in area.

For Comparison: 5.8 million square miles of seasonal sea ice is almost enough to cover the lower 48 United States twice over.

Below: Seasonal differences in Antarctic sea ice extent. Image courtesy of the National Snow and Ice Data Center, University of Colorado, Boulder, Colorado.

Seasons: Winter, Spring, Summer, Fall

Sources: The National Snow and Ice Data Center. “All About Sea Ice” Accessed Online 30 April 2010

Climate Trivia: Arctic and Antarctica

kraus — Mon, 26 Apr 2010 14:48:27 +0000

Over the past century, the Arctic was cooler than normal from 1900-1915, warmer than normal during the 20’s, 30’s and 40’s, cooler than normal during the 50’s, 60’s and 70’s and has been warmer than normal from the early 1980’s to today.

Trivia Question: During warm periods in the Arctic, is the Antarctic generally…

a)   Also warmer than normal
b)   In an opposite cool phase
c)   Antarctic temperatures were steady over the 20th century
d)   No positive or negative relationship between Arctic and Antarctic temperatures exist

The correct answer is b. Periods when the Arctic is warmer than normal tend to be periods when Antarctica is cooler than normal and vice-versa. This “bipolar seesaw” phenomenon has been linked to well-documented shifts in ocean circulation, specifically the 65-70 year Atlantic Multidecadal Oscillation. Strong winds around Antarctica bring salty waters from the ocean depths to the surface. These waters are heated by the sun and Atlantic surface currents take the warm and salty waters North. When this process is at its most efficient, more warm water is transported to the far north, warming the Arctic and cooling the Antarctic. When the process is not efficient, more warm water stays around Antarctica, warming that continent instead of the Arctic. This general pattern has been observed in long-term (millennial) paleo-ice core records. The last 30 years have been different, however, with a dramatically warmer Arctic without a corresponding cooling of the Antarctic.

Seasons: Winter, Spring, Summer, Fall

Source: Chylek, P et al. “Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures.” Geophysical Research Letters 37 (2010): L08703.

Climate Trivia: Ocean Salinity

kraus — Mon, 26 Apr 2010 14:44:45 +0000

Melting ice and intensification of Earth’s water cycle appear to be impacting how salty ocean waters are. How salty the water is affects sea levels as well as Earth’s thermohaline circulation – the ocean currents driven by differences in temperature and salinity. Both changes in sea levels and the thermohaline circulation can have consequences for Earth’s climate.

Trivia Question: Which of the following best characterizes recent trends in ocean surface salinity?

a) Fresher tropics, saltier high-latitudes
b) Fresher Atlantic and Indian Oceans, and a saltier Pacific
c) A fresher Pacific, a saltier Atlantic, and no change in the Indian Ocean
d) Ocean waters are freshening near the poles and getting saltier near the equator

The correct answer is d. Increased input of fresh water into the higher latitude parts of the oceans as glaciers melt and precipitation increases is being largely counteracted by increased evaporation (and thus saltier waters) in the tropics and especially the subtropics. The areas immediately around the Equator are also freshening. The Atlantic Ocean is experiencing a freshening of the waters between 45 and 70 degrees North, as well as in waters near Antarctica. Most of the Indian Ocean, which lies largely in the tropics, is becoming saltier. The Pacific also follows the general rule, with an especially strong freshening around the Equator, and the tropical and subtropical waters are becoming more saline. The far South Pacific and the Indian Ocean around Antarctica are also freshening.

Seasons: Winter, Spring, Summer, Fall

Source: Boyer, TP et al. “Linear Trends in Salinity for the World Ocean, 1955-1998.” Geophysical Research Letters 32 (2005): L01604 and Durack, P and Wijffels, S. “Fifty-year Trends in Global Ocean Salinities and Their Relationship to Broad-Scale Warming.” Journal of Climate Preprint (2010): Accessed Online:

Climate Trivia: It’s All Connected

kraus — Mon, 26 Apr 2010 14:39:40 +0000

Teleconnections occur when an event in one part of the world impacts another part of the world. One frequent source of teleconnections is the El Niño-Southern Oscillation (ENSO). ENSO is the periodic shift in wind patterns and sea-surface temperatures over the tropical Pacific Ocean. ENSO’s teleconnections include control over the number of winter storms impacting the California Coast, the intensity of the South Asian (Indian) Monsoon, and even the wintertime Nor’easters along the Eastern U.S. Seaboard.

Trivia Question: Which is another well-documented climate teleconnection?

a. Flooding in India resulting in sea-level rise around Manhattan
b. Mudslides in California causing snow in Maryland
c. Warm North Atlantic sea-surface temperatures leading to more wildfires in the western U.S.
d. Thunderstorms in Omaha leading to drought in Kazakhstan

The correct answer is c. While there may be some spurious correlation between some of the other events listed, analysis of over 500 years of proxy data from the West illustrates that wildfires there are more frequent when sea-surface temperatures in the North Atlantic are warm. Temperatures in the North Atlantic fluctuate between warm and cool conditions on a period of about 65 years, a phenomenon known as the Atlantic Multidecadal Oscillation.

Seasons: Winter, Spring, Summer, Fall

Source: Maue, Ryan N. “Northern Hemisphere Tropical Cyclone Activity.” Geophysical Research Letters 35 (2009): L05805 and Kitzberger, T et al. “Contingent Pacific-Atlantic Ocean influence on multicentury wildfire synchrony over western North America.” Proceedings of the National Academy of Sciences 104 (2007): 543-548 and eGaetana, AT et al. “Statistical Prediction of Seasonal East Coast Winter Storm Frequency.” Journal of Climate 15 (2002): 1101-1117 and Hirsch, ME et al. “An East Coast Winter Storm Climatology.” Journal of Climate 14 (2001): 882-899 and Eichler, T and Higgins W. “Climatology and ENSO-Related Variability of North American Extratropical Cyclone Activity.” Journal of Climate 19 (2006): 2076-2093 and National Oceanic and Atmospheric Administration: Climate Prediction Center. Accessed Online 7 December 2009 http://www.cpc.ncep.noaa.gov/products/precip/CWlink/stormtracks/eisdiffobs.meta.gif

Climate Number: 18 Degrees Fahrenheit

kraus — Mon, 05 Apr 2010 14:12:00 +0000

Earth 13,000 years ago was in the process of thawing from the coldest part of the last ice age. Then, something sudden and catastrophic happened: within a few decades, northern Europe’s average temperature dropped by 18 degrees Fahrenheit. The sudden cold period that followed is called the Younger Dryas, named after the Arctic tundra wildflower that expanded south across Scandinavia at that time. While this cold period was a global event, its most pronounced effects were experienced in northern Europe. Today, the thermohaline circulation in the North Atlantic is driven by sinking cold and salty waters off the coast of Greenland. As these waters sink, they draw up warm waters from the south. The warm waters bring warm air masses to Europe, keeping the continent warmer than it would otherwise be at its relatively high latitude. As the planet was thawing 13,000 years ago, North America’s Laurentide Ice Sheet was melting. This melt allowed previously ice dammed glacial lakes, such as the now dry Lake Agassiz located in modern day Manitoba, to suddenly drain. Shortly after 13,000 years ago, the ice dam that was keeping Lake Agassiz from draining overland into the Arctic Ocean melted, releasing about 2,300 cubic miles of water (almost 24 years worth of discharge from the Mississppi River!) in less than a year. This drainage upset the balance between salt and fresh water that keeps the sinking in the North Atlantic going. As the sinking suddenly stopped, so did the flow of warm waters and air masses to Europe. The interruption of this flow caused the sudden 18 degree Fahrenheit drop in the northern Europe’s temperature.

For comparison: A sudden 18 degree drop in average temperature is equivalent to the climate of Memphis, Tennessee suddenly becoming like the climate of Chicago, Illinois.

Seasons: Winter, Spring, Summer, Fall

Sources: Murton, JB et al. “Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean.” Nature 464 (2010): 740-743 and “River reveals chilling tracks of ancient flood.” Nature 464 (2010): 657.

Climate Number: 229 Trillion Gallons

kraus — Mon, 05 Apr 2010 14:05:47 +0000

Each year, rivers originating in the surrounding mountains and forests send an average of 229 trillion gallons of freshwater into the Gulf of Alaska. The amount of water flowing into the Gulf and when most of the flow occurs affects how salty the waters in the Gulf are. How salty these waters are affects the currents along the shore, which can impact local weather. Salinity variation has also been linked to primary production in the Gulf, which has implications for salmon populations – an important component of the regional economy. Glaciers cover about 30,000 square miles (18 percent) of the Gulf’s drainage area. Melt water from these glaciers currently accounts for about 47 percent of the freshwater discharge, a percentage that has been growing. Over the last few decades, these glaciers have been increasing their annual contribution to the Gulf waters by an average of one trillion gallons each year.

For comparison: 229 trillion gallons is about double the amount of water in Lake Erie.

Seasons: Spring, Summer, Fall

Source: Neal, EG et al. “Contribution of glacier runoff to freshwater discharge into the Gulf of Alaska.” Geophysical Research Letters 37 (2010): LO6404.

Climate Fact: La Niña and the Great Medieval Droughts

kraus — Mon, 22 Mar 2010 14:52:35 +0000

In Brief: Persistently cool conditions in the eastern tropical Pacific during the Middle Ages led to drought in the southwestern United States.

Conditions in the tropical Pacific influence weather throughout the world. On a cycle of two to seven years, the eastern tropical Pacific moves from cool (La Niña) conditions to warm (El Niño) conditions. While warm and cool conditions generally balance each other during the cycle, paleoclimate proxy data from coral reefs in the tropical Pacific indicates that this is not always the case. For much of the 14th and 15th centuries, for example, La Niñas were much more common than El Niños. La Niña conditions force storm systems to move farther north than they otherwise would be, leaving much of the northern subtropics and midlatitudes dry. This is especially true in what is today the southwestern United States. During the late Middle Ages, persistent La Niña conditions meant limited wintertime precipitation, and frequent “mega-droughts” covered much of the Southwest region.

Seasons: Winter, Spring, Summer, Fall

Source: Burgman, R et al. “Role of tropical Pacific SSTs in global medieval hydroclimate: A modeling study.” Geophysical Research Letters 37 (2010): L06705.

Climate Trivia: El Niño Frequency

kraus — Mon, 08 Mar 2010 15:10:17 +0000

Much of our weather in the United States depends on what is happening in the tropical Pacific Ocean. During an El Niño event, which is happening now, the eastern tropical Pacific is warmer than average. During La Niña events, the eastern tropical Pacific is cooler than average. While South America’s west coast may seem far away, what happens there has been shown to affect weather throughout the United States. El Niño events mean more winter Nor’easters on America’s East Coast. El Niño events also result in a more southerly winter storm track, which means more rain and snow for the Southwest but less for the Pacific Northwest. Hurricane season in the Atlantic is less active during El Niño phases and more active during La Niña phases. An intermediate stage, known as the neutral phase, means more snowfall throughout the Mississippi River basin.

Trivia Question: What phase has been more common over the last 25 years?

a) El Niño
b) La Niña

The correct answer is a. El Niño events have become more common since the mid-1970’s. Duing the 1950’s and 1960’s, La Niña events were more common. See below for a graph of the last 60 years of El Niño (red) and La Niña (blue) event frequency.

Seasons: Winter, Spring, Summer, Fall

Sources: Kim, HM et al. “Impact of Shifting Patterns of Pacific Ocean Warming on North Atlantic Tropical Cyclones.” Science 325 (2009): 77-80 and Twine, TE et al. “Effects of El Niño-Southern Oscillation on the Climate, Water Balance, and Streamflow of the Mississippi River Basin.” Journal of Climate 18 (2005): 4840-4861 and Meehl, GA et al. “Current and Future U.S. Weather Extremes and El Niño.” Geophysical Research Letter 34 (2007) L20704 and Easterling, David. “Observed Climate Variability and Change.” NOAA/National Climatic Data Center. Ashville, NC: 31 January 2007 http://www.ametsoc.org/atmospolicy/documents/Easterling-Observed-Change-Jan-07.pdf and Meehl, GA et al. “Current and Future U.S. Weather Extremes and El Niño.” Geophysical Research Letter 34 (2007) L20704 and Easterling, David. “Observed Climate Variability and Change.” NOAA/National Climatic Data Center. Ashville, NC: 31 January 2007 http://www.ametsoc.org/atmospolicy/documents/Easterling-Observed-Change-Jan-07.pdf.

Climate Number: 2200 Cubic Miles

kraus — Mon, 01 Mar 2010 14:54:42 +0000

Glaciers have a mass balance. Glaciers lose mass by melting during the warm season (primarily the summer months) and gain mass by accumulating snow during the cold season (centered around the winter months). If a glacier accumulates more mass during the cold season than it loses during the warm season, it is said to have a positive mass balance. If it loses more mass than it gains, it is said to have a negative mass balance. Since 1960, it has become more common for glaciers to have negative mass balance years than positive mass balance years, leading to an overall global trend of glacial retreat. It is estimated that since 1960, the world’s glaciers (this does not include the ice sheets on Greenland and Antarctica) have lost about 2200 cubic miles of ice. Because melt water from these glaciers feeds the creeks and rivers that ultimately flow into the ocean, more glacier melt means higher sea levels. About one-third of the recent 3.1 mm average annual sea level rise is due to glacial melt.

For Comparison: An equivalent to 2200 cubic miles of volume is about 36 million Great Pyramids of Giza, or about six million Sears Towers.

Seasons: Winter, Spring, Summer, Fall

Sources: Global Climate Change Impacts in the United States, Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson,(eds.). Cambridge University Press, 2009 and Meier, MF et al. “Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century.” Science Express 19 July 2007 / Page 1 / 10.1126/science.1143906.

Climate Number: 73 Terawatts

kraus — Mon, 01 Mar 2010 14:45:37 +0000

The energy moving in both weather systems and through the wires that power your home can be measured in watts. The Sun heats the Earth causing the fluids of the atmosphere and the oceans to move, creating the winds and currents of Earth’s climate. The vast majority of the energy in the climate system moves through the oceans, where currents of warm and cold waters that dwarf even the largest of Earth’s land rivers transport heat and salt to and from the different ocean basins. Compared to other waters in the Arctic, the Barents Sea, which lies to the north of Scandinavia, has a relatively low amount of seasonal sea ice cover. While the northern portion of the sea freezes over with several feet of ice, the southern portion of the sea remains ice free. A current of water from the North Atlantic brings the basin a sufficient amount of warm water to ward off the Arctic ice’s southerly advance. This current moves about 86 terawatts worth of heat into the Barents Sea, and about 13 terawatts leave the sea through other currents. The remaining 73 terawatts is lost into the atmosphere, making what is known as the Barents Sea Opening a major exit, or release point, for the ocean’s heat storage.

For Comparison: It would take about 61,000 1200 megawatt nuclear power plants – about 140 times the number that exist around the world today – to generate 73 terawatts worth of power. This amount of power is almost 30 times the world’s current electrical generation capacity.

Seasons: Winter, Spring

Sources: Smedsrud, LH et al. “Heat in the Barents Sea: transport, storage, and surface fluxes.” Ocean Science 6 (2010): 219-234 and World Nuclear Association. “Nuclear Power in the World Today.” Accessed Online 28 February 2010

Climate Fact: Midwinter Storm Track Suppression

kraus — Mon, 22 Feb 2010 15:15:29 +0000

The temperature/pressure difference between the equatorial regions and the poles is at its maximum during the winter months. The energy this difference generates is thought to power the “storm tracks,” or the bands in the mid-latitudes where east to west traveling storms (cyclonic high and low pressure systems) are most common. The storm track over the Pacific brings the western U.S. ample rainfall for much of the fall, winter and spring seasons. One aspect of Northern Hemisphere winter storm behavior that has been somewhat of a mystery is the midwinter suppression of the Pacific storm track. The maximum latitudinal temperature/pressure difference during winter, which means more power for the storms, is reflected in the Atlantic storm track being at its strongest during the winter months. Over the Pacific, however, the midwinter corresponds to an average decrease in the number and strength of these storms by 20 and 14 percent respectively compared to the fall and spring months. One possible explanation for this suppression is a wintertime drop in the number of atmospheric disturbances that make their way from the mountains of central Eurasia to the Pacific. These disturbances can become the storms that move across the Pacific to North America. The sheer size of the Eurasian landmass means that the wintertime high pressure centers that sit in the middle of the continent are strong enough to push the warmer and competing air masses far to the south and away from the mountains where these warmer air masses can generate the disturbances that can ultimately become the Pacific storms.

Season: Winter

Source: Penny, S et al. “The Source of the Midwinter Suppression in Storminess over the North Pacific.” Journal of Climate 23 (2010): 634-648.