An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and greenhouse periods, during which there are no glaciers on the planet. Earth is currently in the ice age called Quaternary glaciation. Individual pulses of cold climate within an ice age are termed glacial periods, and intermittent warm periods within an ice age are called interglacials or interstadials.
The cryosphere is an all-encompassing term for the portions of Earth's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps, ice sheets, and frozen ground. Thus, there is a wide overlap with the hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes, clouds, precipitation, hydrology, atmospheric and oceanic circulation.
Mean sea level is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.
Post-glacial rebound is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound and isostatic depression are phases of glacial isostasy, the deformation of the Earth's crust in response to changes in ice mass distribution. The direct raising effects of post-glacial rebound are readily apparent in parts of Northern Eurasia, Northern America, Patagonia, and Antarctica. However, through the processes of ocean siphoning and continental levering, the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets.
The East Greenland Current (EGC) is a cold, low-salinity current that extends from Fram Strait (~80N) to Cape Farewell (~60N). The current is located off the eastern coast of Greenland along the Greenland continental margin. The current cuts through the Nordic Seas and through the Denmark Strait. The current is of major importance because it directly connects the Arctic to the Northern Atlantic, it is a major contributor to sea ice export out of the Arctic, and it is a major freshwater sink for the Arctic.
The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent 26 ka – 20 ka ago. Ice sheets covered much of Northern North America, Northern Europe, and Asia and profoundly affected Earth's climate by causing a major expansion of deserts, along with a large drop in sea levels.
Sequence stratigraphy is a branch of geology, specifically a branch of stratigraphy, that attempts to discern and understand historic geology through time by subdividing and linking sedimentary deposits into unconformity bounded units on a variety of scales. The essence of the method is mapping of strata based on identification of surfaces which are assumed to represent time lines, thereby placing stratigraphy in chronostratigraphic framework allowing understanding of the evolution of the earth's surface in a particular region through time. Sequence stratigraphy is a useful alternative to a purely lithostratigraphic approach, which emphasizes solely based on the compositional similarity of the lithology of rock units rather than time significance. Unconformities are particularly important in understanding geologic history because they represent erosional surfaces where there is a clear gap in the record. Conversely within a sequence the geologic record should be relatively continuous and complete record that is genetically related.
A Heinrich event is a natural phenomenon in which large groups of icebergs break off from the Laurentide Ice Sheet and traverse the Hudson Strait into the North Atlantic. First described by marine geologist Hartmut Heinrich, they occurred during five of the last seven glacial periods over the past 640,000 years. Heinrich events are particularly well documented for the last glacial period but notably absent from the penultimate glaciation. The icebergs contained rock mass that had been eroded by the glaciers, and as they melted, this material was dropped to the sea floor as ice rafted debris forming deposits called Heinrich layers.
In geomorphology a river is said to be rejuvenated when it is eroding the landscape in response to a lowering of its base level. The process is often a result of a sudden fall in sea level or the rise of land. The disturbance enables a rise in the river's potential energy, increasing its riverbed erosion rate. The erosion occurs as a result of the river adjusting to its new base level.
Lincoln Sea is a body of water in the Arctic Ocean, stretching from Cape Columbia, Canada, in the west to Cape Morris Jesup, Greenland, in the east. The northern limit is defined as the great circle line between those two headlands. It is covered with sea ice throughout the year, the thickest sea ice in the Arctic Ocean, which can be up to 15 m (49 ft) thick. Water depths range from 100 m (330 ft) to 300 m (980 ft). Water and ice from Lincoln Sea empty into Robeson Channel, the northernmost part of Nares Strait, most of the time.
An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length. They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet. In Antarctica, the ice streams account for approximately 90% of the sheet's mass loss per year, and approximately 50% of the mass loss in Greenland.
The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial and interglacial periods during the Quaternary period that began 2.58 Ma and is ongoing. Although geologists describe this entire period up to the present as an "ice age", in popular culture this term usually refers to the most recent glacial period, or to the Pleistocene epoch in general. Since Earth still has polar ice sheets, geologists consider the Quaternary glaciation to be ongoing, though currently in an interglacial period.
A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land.
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately 14,060,000 km2 (5,430,000 sq mi) and is known as one of the coldest of oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It has also been described as an estuary of the Atlantic Ocean. It is also seen as the northernmost part of the all-encompassing World Ocean.
The geology of the North Sea describes the geological features such as channels, trenches, and ridges today and the geological history, plate tectonics, and geological events that created them.
Between 1901 and 2018, the average global sea level rose by 15–25 cm (6–10 in), or an average of 1–2 mm per year. This rate accelerated to 4.62 mm/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, thermal expansion of water accounted for 42% of sea level rise. Melting temperate glaciers accounted for 21%, with Greenland accounting for 15% and Antarctica 8%. Sea level rise lags changes in the Earth's temperature. So sea level rise will continue to accelerate between now and 2050 in response to warming that is already happening. What happens after that will depend on what happens with human greenhouse gas emissions. Sea level rise may slow down between 2050 and 2100 if there are deep cuts in emissions. It could then reach a little over 30 cm (1 ft) from now by 2100. With high emissions it may accelerate. It could rise by 1 m or even 2 m by then. In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming amounts to 1.5 °C (2.7 °F). It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F).
During the Pliocene epoch, the Earth's climate became cooler and drier, as well as more seasonal, marking a transition between the relatively warm Miocene to the cooler Pleistocene.
Global or eustatic sea level has fluctuated significantly over Earth's history. The main factors affecting sea level are the amount and volume of available water and the shape and volume of the ocean basins. The primary influences on water volume are the temperature of the seawater, which affects density, and the amounts of water retained in other reservoirs like rivers, aquifers, lakes, glaciers, polar ice caps and sea ice. Over geological timescales, changes in the shape of the oceanic basins and in land/sea distribution affect sea level. In addition to eustatic changes, local changes in sea level are caused by tectonic uplift and subsidence.
Relative sea level is defined as the sea level that is observed with respect to a land-based reference frame. It is often contrasted with eustatic sea level, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level, but also by changes on land such as subsidence and isostatic rebound.
Oceanic freshwater fluxes are defined as the transport of non saline water between the oceans and the other components of the Earth's system. These fluxes have an impact on the local ocean properties, as well as on the large scale circulation patterns.
