| Evolution of the Baltic Sea |
|---|
| Pleistocene |
| Eemian Sea (130,000–115,000 BCE) Ice sheets and seas (115,000–14,000 BCE) |
| Holocene |
| Baltic Ice Lake (14,000–9,670 BCE) Yoldia Sea (9,670–8,750 BCE) Ancylus Lake (8,750–7,850 BCE) Mastogloia Sea (Initial Littorina Sea} (7,850–6,550 BCE) Littorina Sea (6,550–2,050 BCE) Modern Baltic Sea (2,050 BCE–present) |
| Sources. Dates are not BP. |
The Eemian Sea was a body of water located approximately where the Baltic Sea is now during the last interglacial, or Eemian Stage, Marine isotopic stage (MIS) 5e, roughly 130,000 to 120,000 years BP. [1] [2] Sea level was 5 to 7 metres (16 to 23 feet) higher globally than it is today, due to the release of glacial water in the early stage of the interglacial after the Saale glaciation.
Although "Eemian" applies only in this article to the northern European glacial system, some have used the term in a wider sense to mean any high-level body of water in the last interglacial and others use the Russian term Mikulinian for the northern European events. [2] : 158
The Saale glaciation (i.e. Saalian), which preceded the Eemian, was larger and greater in extent during its maximum at about 140,000 years ago than the Weichselian glaciation that followed the Eemian period. [2] : 159 The dates of the Eemian Sea came from the pollen record in sediments studied at diverse points and at the northeastern studied areas are consistent with the sea lasting about 11,000 years. [2] : 160 Western Eemian Sea temperatures were 5 to 6 °C higher than today's Baltic Sea. [3] The last Saalian deposits prior to the Eemian contain pollens consistent with dense pine forest with some deciduous trees. [4] At its greatest extent the Eemian Sea was up to 150 km (93 mi) wide over an length of 2,500 km (1,600 mi). [5] At the Baltic end the sea connected to the North Sea possibly by multiple routes. The marine ingression at Ristinge Klint in the Danish Baltic basin occurred 300 years after the Eemian onset similar to that at Mommark in Denmark. This contrasts with further east and suggests these areas of Denmark had higher elevations at this time than further east. [3] The first transgression that reached Poland, was rapid and appears to have been 300 years odd before the Eemian's usual defined start. [4] Ingression was also late Saalian at Plasumi in Latvia and earliest Eemian on Prangli island off Estonia. [3] This is in contrast to the Amsterdam core studies further south that show as of the late Saalian Holland had temperatures similar to the present, Holland was still under ice tongues at this time with melt fresh water lakes and marine transgression of the Eemian did not start until about 1000 years after the pollen record changed from pine forest. [6] The early Eemian Sea connected with the White Sea along the line of the present White Sea–Baltic Canal. Karelia was inundated and Lakes Ladoga and Onega were mere depressions in the shallow eastern end of the Eemian Sea. [2] : 168 It has been thought that the Baltic connection was wider than the Baltic Sea's present narrow straits and so there was a wide and relatively unobstructed seaway from the Baltic to the Arctic Ocean. [3] It has been suggested without proof that a seaway to the Baltic basin existed across Schleswig-Holstein in northern Germany. [7] [3] Whatever the Eemian sea penetrated deep into northern Germany and southwestern Denmark. [7] There is mollusc evidence that suggest the passage to the White Sea was only open for the first 2,500 years of the Eemian, being closed off north of Lake Onega. [5] [3] This area is known as the Karelina Seaway. [3] Several diatom records from northwestern Russia suggest significant salinity for a much longer period and presently in the eastern Baltic region the Eemian sea-level high-stand is believed to have lasted from about 130,250 to 124,000 years BP. [2] : 172 In Poland there is evidence for two periods of increased salinity about 800 to 3500 years and 6200 to 6600 years after the beginning of the Eemian, suggesting a two-step transgression in the Eemian sea. [4] The Eemian was not the uniformly warm interglacial assumed by some, as there is evidence for at least a period of 2 to 3 °C cooler summers. [8]
Shells of the arctic mollusc Portlandia arctica in sediments often allow the identification of sediments from the Eemian Sea, [2] : 161 but problematically studies need to assign a colder temperature to the eastern Baltic potion of the Eemian Sea than at either the Baltic or White Sea ends. [5] For example during the Eemian the warm water bivalve Lucinella divaricata , which is not presently found north of the southwestern entrance to the English Channel, penetrated far into the Baltic area. [5] Accordingly in the Belt Sea and southern Baltic compared to the present Baltic Sea, temperature was about 6 °C warmer and salinity was 15% higher. [5] [3]
Much of northern Europe was under shallow water. Scandinavia was an island. The salinity of the Eemian Sea was comparable to that of the Atlantic and much more than the present Baltic Sea. [2] : 158 Scientists reach these conclusions from a study of types of micro-organisms fossilized in the clay sediments laid down in the Eemian Sea, and from the included pollen of Corylus , Carpinus and Betula .
During MIS 5e, the mean annual temperature was 3 °C higher than today. This was followed by the cooler MIS 5d, c, b and a, with the region continuing to rise isostatically. Some water was recaptured in ice. At least during the MIS 5d (about 118,000 to 80,000 year ago), the eastern Baltic was free of ice and it is possible that the Weichselian ice sheet only covered the area during the last glacial maximum. Levels in the Eemian Sea dropped, and any remaining opening to the White Sea was blocked. Any post-Eemian brackish lake did not last long, being covered with ice. The Weichselian glaciation starting fully in MIS 4, with an interstadial in 3 and a greatest extent in 2, which produced, at its maximum between 20,000 and 18,000 years BP, an ice sheet more than 3 kilometres (1.9 mi) thick. The ice extended southward into northern Europe as far as France and eastward as far as Poland. After its recession, the Baltic Ice Lake appeared.
The Last Glacial Period (LGP), also known as the Last glacial cycle, occurred from the end of the Last Interglacial to the beginning of the Holocene, c. 115,000 – c. 11,700 years ago, and thus corresponds to most of the timespan of the Late Pleistocene.
The Eburonian, or, much less commonly, the Eburonian Stage, is a glacial complex in the Calabrian age of the Pleistocene epoch and lies between the Tegelen and the Waalian interglacial. The transition from the Tegelen to the Eburonian started about 1.78 million years ago, lasted 480,000 years. In geologic strata, at its base, from its startpoint, the Neogene underlies different Gelasian deposits starkly in much of the Netherlands.
The Last Interglacial, also known as the Eemian, was the interglacial period which began about 130,000 years ago at the end of the Penultimate Glacial Period and ended about 115,000 years ago at the beginning of the Last Glacial Period. It corresponds to Marine Isotope Stage 5e. It was the second-to-latest interglacial period of the current Ice Age, the most recent being the Holocene which extends to the present day. During the Last Interglacial, the proportion of CO2 in the atmosphere was about 280 parts per million. The Last Interglacial was one of the warmest periods of the last 800,000 years, with temperatures comparable to and at times warmer than the contemporary Holocene interglacial, with the maximum sea level being up to 6 to 9 metres higher than at present, with global ice volume likely also being smaller than the Holocene interglacial.
Bolshoy Lyakhovsky Island, or Great Lyakhovsky, is the largest of the Lyakhovsky Islands belonging to the New Siberian Islands archipelago between the Laptev Sea and the East Siberian Sea in northern Russia. It has an area of 5,156.6 km2 (1,991.0 sq mi), and a maximum altitude of 311 m (1,020 ft).
There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period, was the most recent time during the Last Glacial Period where ice sheets were at their greatest extent 26,000 and 20,000 years 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.
The Hoxnian Stage was a middle Pleistocene stage of the geological history of the British Isles. It was an interglacial which preceded the Wolstonian Stage and followed the Anglian Stage. It is equivalent to Marine Isotope Stage 11. Marine Isotope Stage 11 started 424,000 years ago and ended 374,000 years ago. The Hoxnian is divided into sub-stages Ho I to Ho IV. It is likely equivalent to the Holstein Interglacial in Central Europe.
The Wolstonian Stage is a middle Pleistocene stage of the geological history of Earth from approximately 374,000 until 130,000 years ago. It precedes the Last Interglacial and follows the Hoxnian Stage in the British Isles.
Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data derived from deep sea core samples. Working backwards from the present, which is MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are lows in the oxygen-18 figures, representing warm interglacial intervals. The data are derived from pollen and foraminifera (plankton) remains in drilled marine sediment cores, sapropels, and other data that reflect historic climate; these are called proxies.
Littorina Sea is a geological brackish water stage of the Baltic Sea, which existed around 8500–4000 BP and followed the Mastogloia Sea, a transitional stage from the Ancylus Lake.
An interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene interglacial began at the end of the Pleistocene, about 11,700 years ago.
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.
The Baltic Ice Lake is a name given by geologists to a freshwater lake that evolved in the Baltic Sea basin as glaciers retreated from that region at the end of the last ice age. The lake's existence was first understood in 1894. The lake existed between about 16,000 and 11,700 years ago with well defined evidence from the warming of the Bølling–Allerød Interstadial to the period of cooling called the Younger Dryas before the Holocene, the onset of which is close in time to the end of the ice lake. The lake drained into the raising world ocean on two occasions and when water levels became the same on the second, with a sea level passage in the Billingen region of southern Sweden, it became the Yoldia Sea.
Yoldia Sea is a name given by geologists to a variable brackish water stage in the Baltic Sea basin that prevailed after the Baltic Ice Lake was drained to sea level during the Weichselian glaciation. Dates for the Yoldia sea are obtained mainly by radiocarbon dating material from ancient sediments and shore lines and from clay-varve chronology. Such dates tend to vary by as much as a thousand years in the literature, but were corrected in 2021 for the whole of the Holocene. The sea can not have existed before the final drainage to sea level of the Baltic Ice Lake in 11,620 cal. year BP.
The Mastogloia Sea is one of the prehistoric stages of the Baltic Sea in its development after the last ice age. It is characterised by distinctive deposits of the calciferous shell of species of the diatom Mastogloia that were used for paleoenvironmental reconstructions. This transition took place at different times in different parts of the Baltic basin c. 9000 years ago following the Ancylus Lake stage and preceding the full Littorina Sea stage.
Marine Isotope Stage 11 or MIS 11 is a Marine Isotope Stage in the geologic temperature record, covering the interglacial period between 424,000 and 374,000 years ago. It corresponds to the Hoxnian Stage in Britain.
The Saale glaciation or Saale Glaciation, sometimes referred to as the Saalian glaciation, Saale cold period, Saale complex (Saale-Komplex) or Saale glacial stage, covers the middle of the three large glaciations in Northern Europe and the northern parts of Eastern Europe, Central Europe and Western Europe by the Scandinavian Inland Ice Sheet. It follows the Holstein interglacial and precedes the Eemian interglacial, spanning from around 400,000 years ago to 130,000 years ago. The Saalian covers multiple glacial cycles punctuated by interglacial periods. In its latter part it is coeval with the global Penultimate Glacial Period.
The Weichselian glaciation is the regional name for the Last Glacial Period in the northern parts of Europe. In the Alpine region it corresponds to the Würm glaciation. It was characterized by a large ice sheet that spread out from the Scandinavian Mountains and extended as far as the east coast of Schleswig-Holstein, northern Poland and Northwest Russia. This glaciation is also known as the Weichselian ice age, Vistulian glaciation, Weichsel or, less commonly, the Weichsel glaciation, Weichselian cold period (Weichsel-Kaltzeit), Weichselian glacial (Weichsel-Glazial), Weichselian Stage or, rarely, the Weichselian complex (Weichsel-Komplex).
Marine Isotope Stage 5 or MIS 5 is a marine isotope stage in the geologic temperature record, between 130,000 and 80,000 years ago. Sub-stage MIS 5e corresponds to the Last Interglacial, also called the Eemian or Sangamonian, the last major interglacial period before the Holocene, which extends to the present day. Interglacial periods which occurred during the Pleistocene are investigated to better understand present and future climate variability. Thus, the present interglacial, the Holocene, is compared with MIS 5 or the interglacials of Marine Isotope Stage 11.
The geology of the Baltic Sea is characterized by having areas located both at the Baltic Shield of the East European Craton and in the Danish-North German-Polish Caledonides. Historical geologists make a distinction between the current Baltic Sea depression, formed in the Cenozoic era, and the much older sedimentary basins whose sediments are preserved in the zone. Although glacial erosion has contributed to shape the present depression, the Baltic trough is largely a depression of tectonic origin that existed long before the Quaternary glaciation.