Abstract:[1] We evaluate data from the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and Defense Meteorological Satellite Program (DMSP) spacecraft coupled with data from the Super Dual Auroral Radar Network (SuperDARN) polar cap convection patterns in order to study how the ionospheric convection evolves around a sequence of transient, mesoscale flow channel events in the duskside of the cusp inflow region. On a northwestward convection background for the interplanetary magnetic field (IMF) B Y positive an… Show more
“…32 note that the NW-outlet glacier has surge-type behavior, with large ice velocities in 2000–2001 reaching 300–350 m yr −1 followed by a decrease to about 60 m yr −1 in 2005 where the glacier returned to its more quiescent phase. This behavior is supported by radar- and laser satellite altimetry data supplemented with surface mass balance modelling, which combined reveal dynamically driven thickening of the northwestern part of FICC 33 .Figure 6Melt due to open water. ( a ) FIIC in 1978 and (b) 2015.…”
Rising temperatures in the Arctic cause accelerated mass loss from the Greenland Ice Sheet and reduced sea ice cover. Tidewater outlet glaciers represent direct connections between glaciers and the ocean where melt rates at the ice-ocean interface are influenced by ocean temperature and circulation. However, few measurements exist near outlet glaciers from the northern coast towards the Arctic Ocean that has remained nearly permanently ice covered. Here we present hydrographic measurements along the terminus of a major retreating tidewater outlet glacier from Flade Isblink Ice Cap. We show that the region is characterized by a relatively large change of the seasonal freshwater content, corresponding to ~2 m of freshwater, and that solar heating during the short open water period results in surface layer temperatures above 1 °C. Observations of temperature and salinity supported that the outlet glacier is a floating ice shelf with near-glacial subsurface temperatures at the freezing point. Melting from the surface layer significantly influenced the ice foot morphology of the glacier terminus. Hence, melting of the tidewater outlet glacier was found to be critically dependent on the retreat of sea ice adjacent to the terminus and the duration of open water.
“…32 note that the NW-outlet glacier has surge-type behavior, with large ice velocities in 2000–2001 reaching 300–350 m yr −1 followed by a decrease to about 60 m yr −1 in 2005 where the glacier returned to its more quiescent phase. This behavior is supported by radar- and laser satellite altimetry data supplemented with surface mass balance modelling, which combined reveal dynamically driven thickening of the northwestern part of FICC 33 .Figure 6Melt due to open water. ( a ) FIIC in 1978 and (b) 2015.…”
Rising temperatures in the Arctic cause accelerated mass loss from the Greenland Ice Sheet and reduced sea ice cover. Tidewater outlet glaciers represent direct connections between glaciers and the ocean where melt rates at the ice-ocean interface are influenced by ocean temperature and circulation. However, few measurements exist near outlet glaciers from the northern coast towards the Arctic Ocean that has remained nearly permanently ice covered. Here we present hydrographic measurements along the terminus of a major retreating tidewater outlet glacier from Flade Isblink Ice Cap. We show that the region is characterized by a relatively large change of the seasonal freshwater content, corresponding to ~2 m of freshwater, and that solar heating during the short open water period results in surface layer temperatures above 1 °C. Observations of temperature and salinity supported that the outlet glacier is a floating ice shelf with near-glacial subsurface temperatures at the freezing point. Melting from the surface layer significantly influenced the ice foot morphology of the glacier terminus. Hence, melting of the tidewater outlet glacier was found to be critically dependent on the retreat of sea ice adjacent to the terminus and the duration of open water.
“…[] showed by direct observation how pulsed reconnection events lead to a train of flow channels, each new event pushing the older flow channels further into the polar cap. Typical north‐south extent of flow channels tied to newly reconnected flux tubes is ~100–300 km, with east‐west extent exceeding 1000 km [ Lockwood et al ., ; Rinne et al ., ].…”
Section: Observationsmentioning
confidence: 99%
“…This is consistent with a pulsed‐reconnection cusp model [ Lockwood et al ., ], in which PMAFs are tied to distinct reconnected flux tubes with similar but independent history and evolution. Flow channels created by pulsed reconnection have a typical duration of 10–20 min [ Lockwood et al ., ; Rinne et al ., ].…”
Two sequences, before and after magnetic noon, respectively, of poleward moving auroral forms with associated upflows situated above the European Incoherent Scatter Svalbard Radar allowed close study of ion upflow dynamics. We find that flux intensity is correlated with plasma temperature and that upflowing plasma undergoes acceleration proportional to the slope of the velocity profile and to the velocity at each altitude. The potential for upflows to lift thermal plasma to regions where broadband extremely low frequency electric field activity can cause nonthermal acceleration leading to outflow is examined. Equations for estimating the travel time of upflowing plasma are presented. We find that around 40% of the observed upflow profiles with a unit number flux greater than 1 × 10 13 m À2 s À1 can transport plasma from 500 to 800 km altitude in less than 10 min, approximately the typical lifetime of pulsed upflow events. Almost all such profiles can transport plasma from 600 to 800 km in the same time span. Typical transport times for other altitude ranges are also presented. Post magnetic noon the background electron density was somewhat higher than prenoon due to transport of EUV-enhanced plasma, and the postnoon ion flux was somewhat weaker than prenoon.
“…[12] The primary energy deposited into the near-Earth environment by magnetic reconnection events at the magnetopause is dissipation of downgoing Poynting flux into the ionosphere-thermosphere where, by ion frictional drag heating (or equivalently Joule heating as per Thayer and Semeter [2004, Appendix A]), the Poynting flux that is not reflected is nearly all passed into the ultimate heat sink, the thermosphere [Carlson, 2012;Carlson et al, 2012]. Strong plasma flow shears have been known to be common in the cusp for a considerable time [e.g., Pinnock et al, 1993Pinnock et al, , 1995Oksavik et al, 2004aOksavik et al, , 2004bOksavik et al, , 2005Rinne et al, 2007Rinne et al, , 2010Rinne et al, , 2011Moen et al, 2008Moen et al, , 2012aMoen et al, , 2012b. Energy is also deposited by the background cusp particle precipitation, as well as transient injection of electrons and ions precipitating from the newly opened magnetic flux tubes.…”
Section: Relevance Of Magnetic Reconnection Eventsmentioning
[1] We highlight why 630.0 nm auroral emissions excited by thermal electrons are expected to be significant in the cusp and are occurring more often than generally recognized. We note conditions when they are likely to occur and provide a simple formula to calculate the altitude discriminated (R/km) and line-of-sight integrated 630.0 nm intensity (kR). The formula is applied to incoherent scatter radar data near the cusp to produce 2-D maps of thermal red line aurora. We estimate when the thermally excited red aurora should be negligible or not, for given electron density (Ne), electron temperature (Te), and exospheric temperature (Tn) conditions. Sensitivity to Te dominates that to Tn and Ne. We test these formulas against radar and all-sky imaging photometer data for 2 days. The time/ space agreement, as transient strong red arcs pass over the cusp, confirms detection of a thermal 630.0 nm aurora in~400-450 km altitude, twice the height (4 times the area) conventionally assumed for 630.0 nm emissions. Among many potential uses for this technique is application to the long-standing question of the degree to which magnetic reconnection events contribute to the net magnetic flux entering the polar cap. We conclude that it is more often than now recognized and provide a tool and guidelines to facilitate improvement over present underestimates.
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