Problems With The Arctic Record

The Arctic contains many records of past environments that scientists have used to recreate past climates. Bottom water temperatures can be inferred from calcite pseudomorphs such as ikaite (CaCO36H2O), an organic-rich mineral that accumulates in the sediment. Biomarkers such as algae, dino-flagellates, diatoms, and foraminifera are used for their stable isotopes to infer temperature and salinity over the past several million years. The 18O/16O values in these inorganic carbonates reflect sea ice and ice sheet variations through time. These can, in turn, be used to model glacial/interglacial periods. 13C/12C values in planktonic organisms reflect variation in productivity or sediment carbon flux from the surrounding continents.

The unique isolation of the Arctic Ocean may be a factor in maximizing the amplitude of some environmental signals in the sediment record. The water column is more strongly stratified than in most other parts of the world. However, throughout history, as the passageways between the Arctic Ocean and the Pacific and Atlantic Oceans opened and closed, this record was modified. Deep ocean waves may have also modified the sedimentary record. As water currents flow around the ridges on the ocean floor they move the sediment and replace it with sediment from other parts of the sea floor. Bioturbation also plays a role in the modification of the sediment record.

Modification of the sediment in the Arctic Ocean creates even more difficulty in reconstructing the history of this basin. The Arctic has extremely low sedimentation rates, so any disruption in the record could potentially create huge problems with dating and isotope analysis. The sedimentation rate is low in the Arctic for several reasons: the major reason is due to the presence of sea ice. It prevents most, if not all, sediment from settling onto the sea floor anywhere that is covered in ice. This, however, is one way that scientists can reconstruct glacial/interglacial cycles. At the beginning of every interglacial cycle, more sediment accumulates because it is dropped from icebergs and sea ice through melting. This can also be seen in the additional sediment discharge from the Arctic rivers.

Collecting enough material for stable isotope and trace element analysis can also be difficult, especially because during glacial periods when sedimentation and productivity are extremely low, there may not be any biological material to collect. During interglacial periods, there is typically enough material; however, in the event of a melt-water pulse or extreme melting, the amount of sediment is much higher than the number of organisms. This makes picking out acceptable specimens difficult. Dissolution is another problem in the Arctic Ocean. In many locations, any cal-cite will have dissolved before reaching the sea floor without leaving a record to what was present at one time. This also makes comparison across the ocean difficult because dissolution takes places at different times in different areas, creating hiatuses that only appear in certain sediment cores. This is usually caught when material is dated, but the dating of some cores is impossible.

Yet another problem with the oceanic record in the Arctic is the difficulty in getting to it. The field season is short, typically from late July to early October, because of sea ice. Even during this time, an icebreaker is needed to clear a path for ships to pass through, making it expensive and dangerous. Even with an icebreaker, the ice in the central Arctic is too thick to break through, and, therefore, almost impossible to study. Political boundaries also play a role in the scientific study of the Arctic. Seafloor sampling and imaging, especially on the Russian shelves, may be unwanted by foreign governments. This is especially true in areas with natural resources and suspected or known illegal dumping.

As knowledge of this region expands, scientists will gain insight into the dynamics of the past and present world climates. This information can then be used to model future climate changes that will aid in the prediction of how life will need to respond to the changing global climate. However, despite the importance of this region, the Arctic Ocean is one of the least studied places on Earth. Due to the harsh environment and perennial sea ice, this location is difficult to access. The knowledge obtained from sampling is also biased toward effort spent on certain taxa, specific regions, and techniques used for the acquisition of this data. The shallow Arctic shelves are the most studied, especially during the summer months when the sea ice melts back. The Canadian Basin is the least studied because it is covered in ice year round. There is much more that needs to be studied in this complex system of ice, water, land, and life.

SEE ALSO: Biogeochemical Cycles; Climate Models; Climate Sensitivity and Feedbacks; Climatic Data, Ice Observations; Climatic Data, Sea Floor Records; Climatic Data, Sediment Records; Cooperative Institute for Arctic Research; Phyto-plankton; Polar Bears; Sea Ice.

BIBLIOGRAPHY. R. Stein and R. MacDonald, eds., The Organic Carbon Cycle in the Arctic Ocean (Springer-Verlag, 2004); D. Thomas, Frozen Oceans: The Floating World of Pack-Ice (Firefly Books Ltd., 2004).

Ruth Adler Ohio State University

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