Late Warming Research Articles

航空機搭載6GHzマイクロ波放射計と赤外線を用いたアラスカ地表面の冬から春への遷移観測

The rapid Arctic warming has been reported. Winter to spring shift of cryosphere is the key variables to be monitored related to warming mechanism. Satellite remote sensing is effective for observing cryospheric change from winter to spring. Although microwave observations with a frequency of 19 and 37 GHz have conventionally been used for the observation of snow covered areas, this study investigated use of the low-frequency 6 GHz band. To acquire information on the winter‒spring transition of ground conditions in Alaska, flight observations of a forest, wetland and lake were performed using an airborne microwave radiometer. Infrared observation measures surface warming and low frequency microwave can observe inside of snow cover. This combination expands the information on spring snow conditions with warming and melting. The TB from the ground displayed little regional variation in the cold period. The variation increased when the spring snow melting season began. Surface temperature increased during the spring warming period, however, the ground below the snow cover remained cold. Flight and satellite microwave observations provided us with the monitoring capability for the spring warming over Alaska, and illustrate the early warming of lowland and late warming in the mountain areas around Fairbanks. Although inside of snow are still cold in the mountain area, significant warming in the forest, and warming in accelerating at wetland and lake in the low land.

An overview of the Oyashio ecosystem

The Oyashio shelf region and the seasonally ice-covered areas north of Hokkaido are highly productive, supporting a wide range of species including marine mammals, seabirds and commercially important species in the western subarctic Pacific. The fishes include gadids, such as walleye pollock and Pacific cod, and subarctic migratory pelagic fishes such as chum salmon and pink salmon. It is also an important summer feeding ground for subtropical migrants such as the Japanese sardine, Japanese anchovy, Pacific saury, mackerels, Japanese common squid, whales and seabirds. In recent decades, some components of the Oyashio ecosystem (i.e., phytoplankton, mesozooplankton, gadid fish, and subtropical migrants) have shown changes in species abundance or distribution that are correlated with environmental changes such as the 1976/1977 and 1988/1989 regime shifts. The First Oyashio Intrusion moved northward from the mid-1960s until the late 1970s, when it moved southward until the 1980s, after which it returned to the north again after the mid-1990s. The sea-surface temperature in spring decreased after the late 1970s, increased after the late 1980s, and remained high during the 1990s. The extent of ice cover in the Sea of Okhostk also decreased during the latest warming in the 1980–1990s but has increased again since the late 1990s. This and other variabilities affect the Oyashio ecosystem and the surrounding region. r 2007 Elsevier Ltd. All rights reserved.

Late warming and early cooling of the sea surface in the Nordic seas during MIS 5e (Eemian Interglacial)

Geochemical identification of a tephra layer found in two cores from the NE Atlantic Ocean and the SE Norwegian Sea, respectively, and dated to 127 ka BP has enabled us to obtain a precise correlation across the Iceland–Scotland Ridge at the Marine Isotope Stage (MIS) 6/5 transition. The direct distance between the two cores is only about 200 km . South of the Iceland–Scotland Ridge, sea surface temperatures rose abruptly at 130 ka BP at the onset of MIS 5e and at least 2–3000 years earlier than north of the ridge. Maximum sea surface temperatures south of the ridge occurred during this initial phase of MIS 5e, when temperatures in the Nordic Seas were still low. North of the ridge, the sea surface warmed rapidly at 127 ka BP. Correlations between the North Atlantic records and the Eemian of Northwest Europe tentatively indicate that the initial phase of MIS 5e correlates with the early part of the Eemian characterised by a warm, continental type of climate. The period after the warming of the Nordic seas corresponds to the slightly cooler and more oceanic middle Eemian interval in Europe. The sea surface temperatures fell gradually north of the ridge during the later part of MIS 5e and they were low during MIS 5d–5a. South of the ridge the temperatures remained relatively high. The data shows that there was no outflow of deep water from the Norwegian Sea during the later part of MIS 6. Outflow began at the MIS 6/5 transition simultaneous with the sea surface warming south of the ridge.