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The Atlantic Multidecadal Oscillation (AMO), or the North Atlantic’s periodic shift (65-year period) from predominately warm to predominately cool regimes, controls much of the climatic variability in the Northern Hemisphere. During warm (positive) AMO phases, the Northern Hemisphere is generally warmer, by as much as a few degrees Fahrenheit when compared to the cool phases. [...]

During the warm seasons (spring through fall), the water in the Baltic Sea is stable and stratified. This means that the warmest and least dense water is on the surface, and as you dive deeper and deeper, layers of progressively colder, saltier, and denser water are encountered. During the decades of the 1970’s and 1980’s, [...]

Climate variability in the mid- to high-latitudes of the Northern Hemisphere, or the area from about 35 degrees North to the poles, is largely controlled by two naturally occurring climate oscillations, the Pacific Decadal Oscillation (PDO) and the North Atlantic Oscillation (NAO). In 1977, both oscillations shifted from negative to positive phases, which resulted in [...]

Autumn (March to May) rainfall in southeast Australia is important for soil moisture and river recharge because the region is dependent on reliable water sources for cereal crop production. Since 1950, there has been a 40 percent decline in the region’s average autumn rainfall. This has been linked to fewer occurrences of La Niña events, [...]

In the Pacific Northwest, Mountain Hemlocks grow at elevations between 3,600 and 7,500 feet. These shade tolerant trees grow underneath the faster growing but shorter-lived Douglas Firs, and gradually make their way to the top of the canopy over their 700 year life spans. At the region’s high elevations, some of the world’s most extensive [...]

The tropical Pacific basin is one of the planet’s warmest ocean regions, with surface water temperatures rarely falling below 83 degrees Fahrenheit. These perennially warm temperatures provide the fuel for tropical cyclone formation, and the strongest cyclones on record have formed here. Because these waters are already above the threshold for tropical cyclone formation, slight [...]

The Labrador Sea Water (LWS) is a stream of cold, fresh, and oxygen rich water that travels down the western Atlantic coast from the Labrador Sea, which is located between Greenland and Newfoundland, towards the Equator. This stream forms in the late fall/early winter after the seasonal accumulation of glacial melt water, which is less [...]

The Arctic Ocean is surrounded by a series of river drainage basins, which collectively occupy an area 1.5 times that of the ocean basin itself. No other ocean basin’s temperature and salinity levels are more dependent on what happens on the adjacent land surface. These temperature and salinity levels in turn influence the behavior of [...]

About 7,700 years ago, a volcanic eruption 42 times more powerful than the 1980 Mt. St. Helens event happened at Mt. Mazama in the southern Oregon Cascade Mountains. The top 5,000 feet of the mountain collapsed soon afterwards, leaving behind a huge caldera, or crater, which has since filled with about 4.6 trillion gallons of [...]

The El Niño Southern Oscillation (ENSO) cycle, or the cyclical movement of heat in the tropical Pacific Ocean, affects the upper atmosphere over the Atlantic Ocean. This affects both the frequency of Atlantic tropical cyclone formation as well as the positioning of the region’s high and low pressure centers that steer the tropical cyclones. La [...]

The amount of energy that the North Atlantic Basin accumulated over the last 50 years is equivalent to almost four trillion tons of TNT (1.610 × 1022 joules). This energy has not been distributed uniformly, as the tropical and subtropical regions of the North Atlantic have warmed the most, and the subpolar region has actually [...]

The El Niño-Southern Oscillation (ENSO), or the cyclical movement of heat in the tropical Pacific Ocean, affects atmospheric phenomena throughout the world. The cycle affects the strength and position of the Pacific Jet Stream, an upper atmosphere wind current that flows from the Pacific over North America. During La Niña phases of the cycle, the [...]

Over the past century, measurements taken at geologically stable locations show that the global sea level rose by eight inches, with most of this rise happening over the second half of the 20th century. Measurements taken at most coastal locations, however, rarely correspond to this global value because near-shore environments are naturally dynamic. Storms, natural [...]

Seabirds, such as auks, gulls, petrels, terns, and gannets, have spent tens of millions of years adapting to life on the ocean. Some species, such as the Sooty Tern, can spend years at sea before returning to land. The success of these species is dependent on the success of their food sources (such as fish [...]

During the last ice age, an advancing glacier carved out a basin in the Siskiyou Mountains of what is northern California today. As the glacier melted, Castle Lake was formed. Every spring, as the ice on the lake melts and warm water on the bottom of the lake moves to the surface, stirring up nutrients in [...]

The North Atlantic Oscillation (NAO) is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. the low pressure center is especially low and the high pressure center [...]

The North Atlantic Oscillation (NAO), which is part of a large system known as the Arctic Oscillation, is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. [...]

The North Atlantic Oscillation (NAO) is a cyclical change in the difference in atmospheric pressure between a low pressure center around Iceland and a high pressure center around the Azores Islands in the North Atlantic. When this difference in pressure is larger (i.e. the low pressure center is especially low and the high pressure center [...]

A rise in New England’s average temperature over the second half of the 20th Century was accompanied by a decrease in the ratio of precipitation that falls as snow. This trend was strongest for stations in Maine. Between 1949 and 2000, the percentage of annual precipitation? that fell as snow declined from 30 to [...]

Atmospheric carbon dioxide (CO2) levels have risen from 280 parts per million in pre-industrial times to around 385 parts per million today. The rate of this rise has varied from year to year. The two phases of the El Niño Southern Oscillation Cycle (ENSO), El Niño (positive) and La Niña (negative), appear to have a [...]