Masayo Ogi

Impact of the wintertime North Atlantic Oscillation (NAO) on the summertime atmospheric circulation

[1] Using the NCEP/NCAR reanalysis dataset and other observations, we show that the summer high-latitude climate in the Northern Hemisphere is influenced by the NAO of the previous winter. We find this influence in the summertime surface air temperature, the geopotential height, the sea surface temperature (SST), sea-ice/continental snow cover extent fields as well as in the zonal mean geopotential height and zonal wind fields. This summertime NAO signal is annular but its meridional scale is much smaller than the winter annular mode. Distinct summer anomalies are located at the nodal latitudes of the winter anomalies. We suggest that the sea-ice, SST and snow cover anomalies provide the memory allowing the winter NAO to affect the summer climate. INDEX TERMS: 1620 Global Change: Climate dynamics (3309); 1863 Hydrology: Snow and ice (1827); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions. Citation: Ogi, M., Y. Tachibana, and K. Yamazaki, Impact of the wintertime North Atlantic Oscillation (NAO) on the summertime atmospheric circulation, Geophys. Res. Lett., 30(13), 1704, doi:10.1029/2003GL017280, 2003.

The summertime annular mode in the Northern Hemisphere and its linkage to the winter mode

[1] The seasonal variations of the Northern Hemisphere annular mode (NAM) are investigated through empirical orthogonal function analysis of the zonally averaged geopotential height fields for each individual calendar month. Patterns of the winter and summer NAMs differ not only in the geopotential height fields but also in the mean meridional circulation and eddy structure. The summer NAM has a smaller meridional scale and is displaced poleward as compared to the winter NAM. The antinode on the lower-latitude side in the summer NAM is at the nodal latitude of the winter NAM. The summer NAM is more strongly related to surface air temperatures over Eurasia than the original Arctic Oscillation. The summer NAM is a wave-driven internal atmospheric mode that is maintained by both stationary and transient waves. The summer NAM is associated with the Arctic front, polar jet, and storm track around the Arctic Ocean. The winter-to-summer linkage described by M. Ogi et al. can be interpreted as a preferred transition from one polarity of the winter annular mode to the same polarity of the summer annular mode. The spring cryosphere, i.e., snow in Eurasia and sea ice in the Barents Sea, plays a supporting role in this transition. INDEX TERMS: 1620 Global Change: Climate dynamics (3309); 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3319 Meteorology and Atmospheric Dynamics: General circulation; 3349 Meteorology and Atmospheric Dynamics: Polar meteorology; KEYWORDS: Northern Hemisphere’s annular mode, Arctic Oscillation, winter-to-summer link

Replacement of multiyear sea ice and changes in the open water season duration in the Beaufort Sea since 2004

The last decade has witnessed the nine lowest Arctic September sea ice extents in the observational record. It also forms the most recent third of the long-term trend in that record, which reached -13.4% decade-1 in 2015. While hemispheric analyses paint a compelling picture of sea ice loss across the Arctic, the situation with multiyear ice in the Beaufort Sea is particularly dire. This study was undertaken in light of substantial changes that have occurred in the extent of summer multiyear sea ice in the Arctic inferred from the passive microwave record. To better elucidate these changes at a sub-regional scale, we use data from the Canadian Ice Service archive, the most direct observations of sea ice stage-of-development available. We also build upon the only previous sea ice climatological analysis for Canadas western Arctic region by sea ice stage-of-development that ended in 2004. The annual evolution of sea ice by stage of development in Canadas western Arctic changed dramatically between 1983 and 2014. The rate of these changes and their spatial prevalence were most prominent in the last decade. In summer, total sea ice loss occurred via reductions in old and first-year sea ice over increasingly large areas and over more months per year. Resultant delay of thermodynamic freeze up has increased the annual open water duration in the study region. The winter sea ice cover was increasingly composed of first-year sea ice at the expense of old ice. Breakup timing has not significantly changed in the region.

Cold Winter Over North America: The Influence of the East Atlantic (EA) and the Tropical/Northern Hemisphere (TNH) Teleconnection Patterns

Anomalous cold temperatures and strong cyclonic circulation were observed during winter 2013/14 over North America. In this article, we propose for the first time that positive East Atlantic (EA) and positive Tropical/Northern Hemisphere (TNH) patterns were dominant in the winter of 2013/14. The values of the EA and TNH indices for winter 2013/14 were the highest and the second highest for the period of record 1951-2014, respectively. The combined EA and TNH pattern is similar to the corresponding atmospheric circulation observed in the winter of 2013/14. The regression patterns of air temperatures on the EA and TNH index show negative anomalies over North America and the North Atlantic Ocean and positive anomalies over the North Pacific Ocean and the mid-latitude Atlantic Ocean. The regression pattern is similar to air temperature anomalies in winter 2013/14. In addition, the combined EA and TNH pattern correlates with sea surface temperature (SST) anomalies over the North Pacific and North Atlantic that are similar to the winter SST anomalies in winter 2013/14. The EA and TNH teleconnection patterns have contributed to the anomalous atmospheric circulation associated with the extreme cold winter over North America in 2013/14.

Summer-to-Winter Sea-Ice Linkage between the Arctic Ocean and the Okhotsk Sea through Atmospheric Circulation

AbstractContemporary climate science seeks to understand the rate and magnitude of a warming global climate and how it impacts regional variability and teleconnections. One of the key drivers of regional climate is the observed reduction in end of summer sea-ice extent over the Arctic. Here the authors show that interannual variations between the September Arctic sea-ice concentration, especially in the East Siberian Sea, and the maximum Okhotsk sea-ice extent in the following winter are positively correlated, which is not explained by the recent warming trend only. An increase of sea ice both in the East Siberian Sea and the Okhotsk Sea and corresponding atmospheric patterns, showing a seesaw between positive anomalies of sea level pressures over the Arctic Ocean and negative anomalies over the midlatitudes, are related to cold anomalies over the high-latitude Eurasian continent. The patterns of atmospheric circulation and air temperatures are similar to those of the annually integrated Arctic Oscillatio...

The influence of winter and summer atmospheric circulation on the variability of temperature and sea ice around Greenland

Most peripheral seas of the Arctic Ocean have seen a pronounced rise in sea surface temperatures in the past century, and this signature of Arctic amplification in proximity to the land suggests that the observed marine and terrestrial changes might be connected to each other. Using in situ observations of temperature from nine coastal meteorological stations around Greenland (GrSTs) and remotely sensed fields of sea ice extent (SIE), we examine the interannual variations of surface air temperature (T2m) and sea level pressure (SLP) anomalies associated with the GrSTs and SIEs surrounding Greenland, specifically within Baffin Bay, the Greenland Sea and Kara-Barents Seas. During winter, the interannual variation in T2m and SLP of the west and south coasts of GrSTs and the Baffin Bay SIE are different from that of the east coast of GrSTs and the SIEs in the Greenland Sea and Kara-Barents Seas. The GrSTs on the west and south coasts of Greenland and the Baffin Bay SIE are associated with the T2m anomalies over Baffin Bay and Davis Strait. The winter SLP patterns associated with these GrSTs and SIEs show positive anomalies over the Arctic and negative anomalies over the North Atlantic with a large-scale atmospheric circulation such as the winter NAO. On the contrary, the east coast of GrSTs and the SIEs in the Greenland Sea and Kara-Barents Seas are correlated with the T2m anomalies over the Greenland Sea and Barents Sea. The surface wind pattern associated with the SIEs in the Greenland Sea and Kara-Barents Seas has a cyclonic circulation in the Greenland Sea and Barents Sea. At the local scale the cyclonic circulation could induce negative SIE anomalies and contribute to increasing open water in the Greenland Sea and Barents Sea. The effect of the loss of sea ice and the heat from the open ocean warming to the atmosphere may influence the GrSTs in the east coast of Greenland. As a result, the T2m pattern associated with the GrSTs in the east coast of Greenland is similar to the pattern of the SIEs in the Greenland Sea and Kara-Barents Seas. During summer, the T2m anomalies associated with all GrSTs and SIEs have positive anomalies over mid-latitudes. The two times series of all GrSTs and SIEs fluctuate quickly and display large trends towards warming temperatures and decreasing SIE. The summer SLP associated with all GrSTs and SIEs are characterised by a seesaw pattern between positive anomalies over the Arctic and negative anomalies over mid-latitudes. The summer SLP anomalies are similar to the summer AO pattern, and it is noteworthy that the summer anticyclonic circulation over the Arctic and Greenland has contributed to the variability and trends in both summer GrSTs and SIEs.