For comparison: Global sea level is rising at about 2.1 millimeters per year, or a little over one-sixteenth of an inch.

Seasons: Winter, Spring, Summer, Fall

Sources: Overeem, I et al. “Sea ice loss enhances wave action at the Arctic coast.” Geophysical Research Letters 38 (2011): L17503 and National Snow and Ice Data Center: Arctic Sea Ice News and Analysis. Accessed Online 28 January 2011 <http://nsidc.org/arcticseaicenews/> and Francis, OP et al. “Ocean wave conditions in the Chukchi Sea from satellite and in situ observations.” Geophysical Research Letters 38 (2011): L24610.

For comparison: Including energy for transport, manufacturing, heating and cooling, residential electricity, etc., it takes about 324 billion watts to power the United States. That is about 1/4000th of the 1.3 petawatts of power in the Atlantic Ocean’s northward heat transport.

Seasons: Winter, Spring, Summer, Fall

Sources: Energy Information Administration. Annual Energy Review, 2010. Accessed Online 28 January 2012 <http://www.eia.gov/totalenergy/data/annual/index.cfm> and Send, Uwe et al. “Observation of decadal change in the Atlantic meridional overturning circulation using 10 years of continuous transport data.” Geophysical Research Letters 38 (2011): L24606.

Rains in East Africa primarily fall during the long rains (March through May) and the short rains (October through December). Understanding how climate and climate change influence these rains is particularly important for predicting drought in the region.  Conditions in the tropical Pacific affect weather throughout the world and the tendency for the tropical Pacific to persist in either cool La Niña phases or warm El Niño phases enable forecasters to predict whether seasonal temperatures or precipitation levels will be above or below average. In addition to local Indian Ocean sea surface temperatures, the short rains in East Africa are strongly influenced by conditions in the tropical Pacific, with La Niña phases leading to reduced precipitation. How the tropical Pacific affects the long rain season, on the other hand, is harder to identify. Recent work shows that since 1999, the long rains have been consistently weak and unable to compensate for reduced short rain precipitation during La Niña phases, leading to drought conditions like those experienced in 2011. Also since 1999, there has been a pattern of consistently elevated sea surface temperatures in the western tropical Pacific and consistently high rainfall levels in that region. The tendency of ocean surface temperatures to remain in particularly warm or cool conditions for relatively long periods of time, coupled with what is known about the atmospheric links between the western tropical Pacific and East Africa, enables forecasters to better understand and predict droughts there.

Seasons: Winter, Spring, Summer, Fall

Source: Lynn, B and DeWiltt, DG. “A recent and abrupt decline in the East African long rains.” Geophysical Research Letters 39 (2012): L02702. 

Earth’s ocean is mixed by a complex system of currents. Downwellings occur when currents move water from the surface to the depths and upwellings occur when nutrient-rich waters are pulled from the depths to the surface. Upwelling areas are some of the most productive waters in the world, including the California Coast where part of the California Current System upwells. The waters along the California Coast are more or less productive during some years, based on the strength and timing of this upwelling. Waters are less productive during years when the winter upwelling is delayed and weaker. This upwelling strength is indexed by the North Pacific Gyre Oscillation (NPGO) – in positive NPGO years, the upwelling starts about six weeks earlier than negative NPGO years. The NPGO is an expression of the variability in the pressure difference between a high pressure center located near Hawaii and a low pressure center in the Gulf of Alaska. This variability leads to changes in the strength and position of the winds that run along the California Coast and work to “pull” a current of water from the depths. Compared to negative NPGO years, average end of winter water conditions during positive NPGO years feature nitrate concentrations that are about 25 percent higher, chlorophyll concentrations about 15 percent higher and zooplankton numbers that are about 20 percent higher. These nutrients and zooplankton  feed commercially-important fish species and seabirds.

Seasons: Winter, Spring

Sources: Chenillat, F et al. “North Pacific Gyre Oscillation modulates seasonal timing and ecosystem functioning in the California Current upwelling system.” Geophysical Research Letters 39 (2012): L01606 and Di Lorenzo, E et al. “North Pacific Gyre Oscillation links ocean climate and ecosystem change.” Geophysical Research Letter 35 (2008): L08607.

Seasons: Winter, Spring, Summer, Fall

Source: Kinnard, C et al. “Reconstructed changes in Arctic sea ice over the past 1,450 years.” Nature 479 (2011): 509-512.

For comparison: 0.40 X 10²² joules is about ten times the amount of excess energy that is being absorbed by the atmosphere. It is also about nine times the amount of energy in 90 billion tons of oil.

Seasons: Winter, Spring, Summer, Fall

Source: Levitus, S et al. “Global ocean heat content 1955-2008 in light of recently revealed instrumentation problems.” Geophysical Research Letters 36 (2009): L07608.

For comparison: The sudden 5,300,000 cubic feet per second surge of freshwater is almost ten times the average flow of the Mississippi River at Baton Rouge, Louisiana, and slightly less than half of the record flow for that location.

Seasons: Winter, Spring, Summer, Fall

Source: Sionneau, T et al. “Provenance of freshwater pulses in the Gulf of Mexico during the last deglaciation.” Quaternary Research 74 (2010): 235-245 and Tarasov, L and Peltier, WR. “A calibrated deglacial drainage chronology for the North American continent: evidence of an Arctic trigger for the Younger Dryas.” Quaternary Science Reviews 25 (2006): 659-688.

The Arctic, where the temperature rise has been twice the global average, has born some of the most visible impacts of the last 40 years of warming. Melting permafrost on land and melting sea ice in the water, the release of methane that had formerly been locked frozen in the tundra, a retreating Greenland Ice Sheet and melting glaciers, the movement of trees into zones formerly too cold to support trees, and the movement of more temperate marine species into the Arctic Ocean have all been observed. Another impact is the degradation of silt ocean cliffs, particularly those along Alaska’s Beaufort and Chuckchi Seas. Local residents, many of whom are descendants of people who lived in the same region thousands of years ago, have houses and other important structures on these cliffs. These cliffs also support infrastructure that is part of the National Petroleum Reserve – Alaska. These silt cliffs have always been subject to erosion from wave action, but have for the most part been immune to complete collapse. This began to change as waters sufficiently warm to melt the ice that holds them together began to appear over the past 40 years, and as the sea ice began to retreat to minimums unprecedented in modern history. Between 1979 and 2009 the number of open water days along the coast (days without ice masses protecting the cliffs from waves) increased from an average of 45 to 95 days, allowing more storms and high-wave events to bring warm, ice melting waters to the cliffs. The average coastal erosion rate of 28.5 feet during the 1980s and 1990s increased to 45 feet per year during the 2000s.

Seasons: Summer, Fall

Source: Overeem, I et al. “Sea ice loss enhances wave action at the Arctic coast.” Geophysical Research Letters 38 (2011): L17503.

For comparison: The 34 cubic miles of groundwater sent to the oceans raises global sea levels by 0.39 millimeters each year, which is a significant fraction of the total 2.1 millimeter annual sea-level rise. Sea level rise from the water coming off the shrinking Greenland and Antarctic Ice Sheets is about 1.3 millimeters per year.

Source: Church, JA et al. “Revisiting the Earth’s sea-level and energy budgets from 1961 to 2008.” Geophysical Research Letters 38 (2011): L18601.

A system of big warm and cool water ocean currents, which dwarf the flow of even the largest rivers, work to mix heat and nutrients around the globe. This circulation is ultimately driven by two things: differences in heat and salt content in the water, and prevailing winds, which can generate currents as they move across the ocean surface. One crucial process for the whole system, the Atlantic Meridional Overturning Circulation (AMOC), happens in the far North Atlantic near Greenland. A flow of warm and very salty water from the south cools as it moves towards the pole. Once it becomes sufficiently cool and salty, and thus sufficiently dense, it sinks and becomes a cool deep water current heading south. Why does this same process not happen in the Pacific Ocean? The presence of the Rocky Mountains in North America and the Andes Mountains in South America block the westerly winds blowing moisture from the Pacific towards the Atlantic, reducing the amount of rainfall and freshwater the Atlantic gets. On the other hand, the Atlantic’s trade winds, which move over the mountain gaps of the thin Central American Isthmus, do bring moisture to the Pacific. This unequal exchange means the Pacific Ocean is dominated by a freshwater surface layer sitting on top of dense salty water, as opposed to in the Atlantic, where there is mobile salty surface water. Without the presence of these mountains, our oceans and climate would function quite differently.

Source: Schmittner, A et al. “Effects of Mountains and Ice Sheets on Global Ocean Circulation.” Journal of Climate 24 (2011): 2814-2829.

Florida Keys National Marine Sanctuary, the nation’s second largest marine sanctuary, provides a breeding ground for 5,500 species. This marine life supports a 20 million pound per year fishery and a coral reef tourism industry valued at 4.4 billion dollars. The richest parts of the sanctuary occur around coral reefs. While these reef ecosystems host some of Earth’s most visually stunning species, it is the microscopic, single-celled organisms called zooxanthellae that make these ecosystems possible. Zooxanthellae live inside the coral and pay “rent” by manufacturing sugars, which feed the coral. About 90 percent of the coral’s energy needs are provided by zooxanthellae. When ocean waters become too warm, however, corals expel zooxanthellae and “bleach,” losing their primary food source. Sea surface temperatures in the tropical and subtropical Atlantic are the warmest they have been since record keeping began in the 1880s. The last 15 years have been particularly hard on coral; in 1996 about 11.7 percent of the sanctuary was covered with living coral, but by 2005, too many frequent and prolonged periods of water temperatures exceeding 86 degrees Fahrenheit had reduced coral cover to 6.7 percent – a 180 square mile decrease in coral cover.

A likely contributor to this coral stress has been rising atmospheric carbon dioxide (CO2) levels. The oceans absorb excess carbon dioxide, about 22 million tons each day, and become more acidic as a result. More acidic waters mean less carbonate is available for coral, which need the carbonate to build their bodies. Ocean waters have become 30 percent more acidic in the last 200 years as the waters have absorbed an estimated 525 billion tons of CO2. How coral react to more acidic waters is influenced by the surrounding water temperature, with warm waters exacerbating the effect of increased acidity.

Seasons: Winter, Spring, Summer, Fall

Sources: United Nations Atlas of the Oceans: The Value of Coral Reefs. Accessed Online 8 October 2007: http://www.oceansatlas.com/ and 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 <http://www.sciencedaily.com/releases/2009/02/090223091752.htm> and Moy, AD et al. “Reduced calcification in modern Southern Ocean planktonic foraminifera.” Nature Geoscience 2 (2009): doi:10.1038/ngeo460  and 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 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 and Gaskill, Melissa. “Global bleaching goes from bad to worse.” Nature News 19 November 2010. Accessed Online 18 September 2011 < http://www.nature.com/news/2010/101119/full/news.2010.621.html>.

The Red Sea, which separates Africa from the Arabian Peninsula, hosts one of Earth’s most diverse marine ecosystems. The diversity in the Red Sea is particularly impressive because it is one of the least explored marine ecosystems, meaning that there are likely lots of life forms yet to be discovered there. The Red Sea’s diversity is largely due to the 1,240 miles of coral reefs that run near the sea’s shore. Coral reefs are considered the “rainforests of the ocean,” with the coral creating a matrix providing habitat for thousands of other species. One of the species, which actually inhabits coral bodies, is a type of algae called zooxanthellae. This algae has a symbiotic relationship with the coral: the coral provide a place to live, and the algae provide the coral with nutrients through photosynthesis, the process through which plant like species use the Sun’s energy to turn water and carbon dioxide into sugar. While coral can only survive in warm ocean waters, if temperatures become too warm the coral do not grow as well because the algae do not photosynthesize as efficiently. The already warm Red Sea has warmed at a particularly rapid rate over the last two decades. The ocean surface there is about 1.3 degrees Fahrenheit warmer today than it was in the early 1980s, with an abrupt temperature increase happening after 1994. This warming has been accompanied by a 30 percent decline in coral growth.

Sources: Raitsos, DE et al. “Abrupt warming of the Red Sea.” Geophysical Research Letters 38 (2011): L14601 and Cantin, NE et al. “Ocean Warming Slows Coral Growth in the Central Red Sea.” Science 329 (2010): 322-325.

The last interglacial period (LIG), which ran from about 130,000 to 120,000 years ago, was a particularly warm interglacial period with global temperatures about 3.6 degrees warmer than today. Sea levels during the LIG were about 23 feet higher than current Holocene (the last 10,000 years) levels, despite global sea surface temperatures not being much warmer than today (perhaps 1.3 degrees Fahrenheit warmer). This lack of a major water temperature difference implies that only a small fraction – about a foot or two – of the 23-foot sea level rise was due to thermal expansion of the ocean waters, which happens as the ocean collects heat and the water molecules become more energetic. For comparison, about one-third of the eight-inch sea level rise experienced during the 20th century was due to thermal expansion; melting of mountain glaciers and the Greenland and Antarctic ice sheets accounted for the rest. In addition to thermal expansion, estimates of sea level rise sources during the LIG suggest that less than one-third was from Greenland and mountain glaciers, and at least two thirds was from the Antarctic Ice Sheet. This implies that the stability of the Antarctic Ice Sheet may be particularly sensitive to temperature rises.

Source: McKay, NP et al. “The role of ocean thermal expansion in Last Interglacial sea level rise.” Geophysical Research Letters 38 (2011): L14605.  

Water conditions along the Pacific Northwest coast are controlled by the Northern California Current (NCC) system, which features a strong alongshore northward flow of warm waters during winter and a southward flow of cool waters during the summer. On longer time scales, the Pacific Decadal Oscillation (PDO) is a cycle where abnormally warm and abnormally cool conditions shift across the North Pacific. During positive PDO phases, warm conditions in the northeastern Pacific accompany a stronger wintertime northward flow in the NCC that favors the survival of warm water plankton, fish and even seabird species in places as far north as Vancouver Island, Canada. Negative phases with cool conditions feature stronger summertime southward flows that favor the survival of cool water plankton, which tend to be richer in fats and more nutritious than their warm water counterparts. This variability in nutrition levels in the waters influences the survival rates of juvenile salmon, which enter the ocean and begin feeding on plankton in April and May, just after the current shifts. These salmon return upstream a year and a half later in the autumn to spawn in the place they were born. Water samples taken off the coast of Newport, Oregon during different phases of the PDO were used to analyze associated changes in plankton community compositions and then compared to Coho salmon survival rates. Years when more fat-rich plankton species were present were years when juvenile Coho salmon survival rates were the highest.

Seasons: Winter, Spring, Summer, Fall

Source: Hongsheng, B et al. “Transport and coastal zooplankton communities in the northern California Current system.” Geophysical Research Letters 38 (2011): L12607.

For comparison: 92 gigatons is about the same weight as 250,000 Empire State Buildings.

Seasons: Spring, Summer, Fall

Source: Gardner, AS et al. “Sharply increased mass loss from glaciers and ice caps in the Canadian Arctic Archipelago.” Nature 473 (2011): 357-360.

• The oceans are currently absorbing about 22 million tons of carbon dioxide (CO2) each day?
• The oceans have absorbed an estimated 525 billion tons of CO2 over the last 200 years?
• As oceans take CO2 out of the atmosphere, the waters become more acidic?
• On the pH acidity scale (which ranges from zero to 14, with zero being the most acidic and seven being neutral) the world’s oceans have fallen from a pH of 8.2 in the late 18th century to a pH of 8.1 today, a 30 percent increase in acidity?
• The tiny planktonic foraminifera that live in the Southern Ocean around Antarctic have shells that 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 <http://www.sciencedaily.com/releases/2009/02/090223091752.htm> and Moy, AD et al. “Reduced calcification in modern Southern Ocean planktonic foraminifera.” Nature Geoscience 2 (2009): doi:10.1038/ngeo460.

For Comparison: When sea levels were 23 feet higher, South Florida was likely under water, as was Louisiana’s Bayou. Cities like Baltimore, parts of Washington, DC, Boston, the Norfolk/Hampton Roads area and the Outer Banks were likely submerged as well. The Jutland Peninsula in Denmark was probably cut off from mainland Europe and enough of Scandinavia would have been submerged to allow the Baltic Sea to join the Arctic Ocean.

Seasons: Winter, Spring, Summer, Fall

Sources: Denton, GH et al. “The Last Glacial Termination.” Science 328 (2010): 1652-1655 and Kopp, RE et al. “Probabilistic assessment of sea level during the last interglacial stage.” Nature 462 (2009): 863-868.

The eruption of Iceland’s Laki volcano from June 8, 1783 to February 1784 had widespread and devastating consequences the world over. The event was one of the biggest natural disasters in British history, with sulfuric acid gas fumes killing over 23,000 Britons. The gas plume initially caused heat waves in Europe before spreading around the globe and cooling the rest of the Northern Hemisphere. Both France and Japan experienced crop failures and famines that year, and Alaskan tree ring records tell of a remarkably cold summer in North America. The Inuit remember it as “the summer that did not come.” The following winter was remarkably cold as well, with Europe being around 3.6 degrees Fahrenheit below normal and eastern North America having temperatures 8.6 degrees Fahrenheit below the 225 year mean. Early Americans skated on the harbor ice of Charleston, South Carolina, the Mississippi River was frozen at its delta, ice floes floated through the Gulf of Mexico and the Chesapeake Bay had its longest freeze-over on record. But was this severely cold winter caused by Laki’s eruption? According to tree ring proxy records used to reconstruct conditions in the tropical Pacific Ocean and North Atlantic over the centuries before instrumental data, at least part of the winter’s severity was due to a strong El Niño in the tropical Pacific and a strongly negative North Atlantic Oscillation (NAO). The strong El Niño event shifted storm tracks to the south, bringing frequent winter storms to the southern United States, while the strongly negative NAO allowed frigid Arctic air masses to easily sweep southward into the mid-latitudes. The coincidence of these conditions, as a result of serendipitous sea surface temperature variability, is similar to what happened during the 2009-2010 winter, which brought record cold to parts of the United States.

Seasons: Winter, Spring, Summer, Fall

Source: D’Arrigo R, et al. “The anomalous winter of 1783-1784: Was the Lake eruption or an analog of the 2009-2010 winter to blame?” Geophysical Research Letters 38 (2011): L05706.

For Comparison: About eight gigatonnes of carbon are emitted from human fossil fuel use each year. Five gigatonnes is about the same weight as 900 Great Pyramids at Giza.

Seasons: Winter, Spring, Summer, Fall

Source: Henson, SA et al. “A reduced estimate of the strength of the ocean’s biological carbon pump.” Geophysical Research Letters 38 (2011): L04606.

Seasons: Winter, Spring, Summer, Fall

Source: Brierley, CM and Fedorov, AV. “Relative importance of meridional and zonal sea surface temperature gradients for the onset of the ice ages and Pliocene-Pleistocene climate evolution.” Paleoceanography 25 (2010): PA2214.