By LiveScience Staff

A reconstruction of sea ice reveals the lowest levels in 800 years, according to new research published in the journal Climate Dynamics.

Researchers modeled sea ice levels between Greenland and Svalbard, an archipelago in the Arctic Ocean north of Europe, from the 13th century to present using data from a natural climate "archive" and from historic human records.

Sea ice melting and re-freezing is a complicated process that is influenced by a number of factors such as wind patterns, ocean currents, and how much ice has frozen or melted in recent years. The authors did not point to any causes for the changes in sea ice levels in their study.

The scientists noted that even though the 13th century was a relatively warm period and ice levels were low then, 20th century sea ice levels are still the lowest. The "Little Ice Age," from 1700 to 1800 had the greatest cover of sea ice, according to their data.